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HANDBOOK 

FOR 

HEATING AND VENTILATING 
ENGINEEKS 



JAMES D" HOFFMAN, M. E. 

PROFESSOR OF MECHANICAL ENGINEERING AND PRACTICA7> 

MECHANICS, UNIVERSITY OF NEBRASKA 

MEMBER AND PAST PRESIDENT A. S. H. & V. E. 

MEMBER A. S. M. E. 

ASSISTED BY 

BENEDICT F. RABER, B. S., M. E. 

ASSISTANT PROFESSOR OF MECHANICAL ENGINEERING 
UNIVERSITY OF NEBRASKA 



McGRAW-HILL BOOK COMPANY 
239 WEST 39TH STREET, NEW YORK 

6 BOUVERIE STREET. LONDON, E. 0. 

1913 



.Hi 



Copyright, 1913 

BY 

James D. Hoffman 



(First Edition: Copyright, 1910, 
By James D. Hoffman) 



/? 

-^-/9^. 



/=?. 



iTt) 



OCI.A3514 20 
/60/ 



EXTRACT FROM PREFACE TO FIRST EDITION. 

In the development of Heating and Ventilating work, it 
Is highly desirable that those engaged in the design and the 
installation of the apparatus be provided with a hand-book 
convenient for pocket use. Such a treatise should cover the 
entire field of heating and ventilation in a simplified form 
and should contain such tables as are commonly used in 
every day practice. This book aims to fulfill such a need and 
is intended to supplement other more specialized works. Be- 
cause of the scope of the work, its various phases could not 
be discussed exhaustively, but it is believed that all the fun- 
damental principles are stated and applied in such a way as 
to be easily understood. It is suggestive rather than diges- 
tive. The principles presented are the same as those that 
have been stated many times before, but the arrangement of 
the work, the applications and the designs are all original. 
Many formulas and rules are necessarily given; but it will 
be seen that, in most cases, they are developments from a few 
general formulas, all of which can be readily understood and 
remembered. Practical points in constructive design have 
also been considered. However, since the principles of heat- 
ing and ventilation are founded upon fundamental thermo- 
dynamic laws, it seems best to accentuate the theoretical 
side of the work in the belief that if this is well understood, 
practical points of experience will easily follow. A pamphlet 
containing suggestions and problems for a course of instruc- 
tion in technical schools is included with every book. 

It is hoped that the material here given will be simple 
enough for the beginner and, at the same time, sufficiently 
complete and exact for the engineer with years of experience. 
If it merits the approval of the reader, or if any part is de- 
fective or misleading, we trust that statements of criticism 
will be freely contributed. The only way to perfect such a 



book is to have the good wishes and the co-operation of en- 
gineers in all branches of the work. These are solicited. 

All the standard works upon the subject have been freely 
consulted and used. In most cases where extracts are made, 
acknowledgment is given in the text. In addition to this, 
references for continued reading are quoted at the close of 
each important topic. Because of these references through- 
out the book, we do not here repeat the names of their 
authors. We wish, however, to express our sincere apprecia- 
tion of their valuable assistance. 

J. D. H. 



PREFACE TO SECOND EDITION. 

The demand for copies of the first edition of the hand- 
book was so great as to make a second edition necessary 
within the second year after publication of the first edition. 
A few corrections were made on the first edition and all 
the material has been revised to bring it up to date. The 
work on air conditioning has been amplified. The descrip- 
tions of hot water and steam heating have been improved 
by diagrams of the various piping systems. Two chapters 
have been added on refrigeration and many tables have 
been added in the Appendix. Many suggestions have come 
from men in practice and these suggestions have been con- 
sidered, thus enlarging upon the practical side and the ap- 
plications. It is believed now that every subject discussed 
within the -scope of the book has been revised to meet the 
present state of the science. 

Lincoln, Neb. J- !>• H. 



CONTENTS 



CHAPTER I. (Heat) 
Arts. Pages 

1- 4 Introductory. Measurement of Heat and 

Temperatures 9- 13 

5 Radiation, Conduction, Convection 14- 15 

CHAPTER n. (Air) 
6- 9 Composition of Air. Amount Required per 

Pertson 16- 24 

10- 13 Humidity 25- 30 

14- 15 Convection of Air. Measurement of Air Ve- 
locities 31- 34 

16- 20i Air Used in Combustion. Chimneys 35- 37 

References on Ventilation 38 

CHAPTER in. (Heat Losses) 
21- 29 Heat Losses from Buildings 39- 47 

30 Teimperatures to be Considered 47- 48 

31 Heat given off from Lights and Persons. ... 49 
References on Heat Losses from Buildings. . 50 

CHAPTER IV. (Furnace Heating) 

32- 34 Essentials of the Furnace System 51- 53 

35- 37 Air Circulation in Furnace Heating 53- 55 

38- 47 Calculations in Furnace Design 56- 61 

48 Application to a Ten Room Residence 62- 66 

CHAPTER V. (Furnace Heating, Continued) 

49- 51 Selecting, Locating and Setting the Furnace 67- 71 

52- 57 Air Ducts. Circulation of Air in Rooms.... 71- 76 

58 Fan-Furnace Heating 77 

59 Suggestion;s for Operating Furnaces 78- 79 

60 Best Outside Temperature 79- 83 

References on Furnace Heating 84 

C:7HAPTER VL (Hot Water and Steam Heating) 
61- 66 Comparison and Classification of Systems... 85- 90 

67 Diagrams of Piping Systems 91- 95 

68 Accelerated Systems 95- 99 

69 Vacuum Systems for Steam 99-102 

CHAPTER VIL (Ht. Water and St. Heating, Cont'd) 
70- 75 Claissificati'on and Efficiencies of Radiators .. 103-108 
76- 79 Heaters and Boilers. Combination Systems. 

Spittings 108-113 



CHAPTER VIII. (Ht. Wfei.ter and St. Heating Cont'd) 

Arts. Pages 

80- 83 Calculation of Radiator Surface 114-121 

83- 86 Pipe Sizes. Grate Area. Piping- Connections . 121-124 

84 General Application to Hot Water Design. . .125-131 

88- 89 Insulating Steam Pipes. Water Hammer ... 131-133 

90 Feeding Return Wiater to Boiler 133-137 

91 Suggestions for Operating Boilers 137-138 

References on Hot Water and Steam Heat'g 139-140 

CHAPTER IX. (Mechanical Vacuum Heating) 

92- 96 General. Webster, Van Auken. Automatic 

and Paul Systems 141-151 

97 References on Mechanical Vacuum Heating 152 

CHAPTER X. (Mechanical Warm Air Heating) 
98-104 General Discussdon. Blowers and Fans. 

Heating Surfaces 153-165 

105-107 Single and Double Duct Systems. Air Wash- 
ing 165-168 

CHAPTER XI. (Mech. Warm Air Heating, Cont'd) 

'108-112 Heat Loss. Air Required. Air Tempera- 
tures 169-172 

113-114 Air Velocities. Area of Ducts 172-173 

115-120 Heating Surface in Coils. Arrangenient of 

Coils 173-183 

121-122 Amount of Steam Used in the System 183 

CHAPTER XII. (Mech. Warm Air Heating, Cont'd) 

123-129 Air Velocity and Pressvire. Horse-Power in 

Moving Air • 184-195 

130-133 Fan Drives. Speeds. Size of Engine. Piping 

Connections 195-200 

134 General Application to Plenum System 200-205 

References on Mechanical Warm Air Heat- 
ing 206-207 

CHAPTER XIII. (District Heating) 
135-139 General. Conduits. Expansion Joints. 

Anchoo-s 208-222 

140-14i2 Typical Design. Heat in Exhaust Steam 222-228 

143-146 Hot Water Systems. General Discussion. ... 229-231 
147-149 Pressure and Velo€lty of Water in Mains. . . .231-235 

150-154 Radiation Heated by Exhaust Steam 236-238 

155-160 Reheating Calculations 238-244 

161-164 Circulating Pumps. Boiler Feed Pumps. ... 244-251 
165-169 Radiation Supplied by Boilers and Economiz- 
ers 251-255 

170 Total Capacity of Boiler Plant 255-258 

171-173 Cost of Heating from Central Station 258-263 

174 Steam System. General Discussion 264-265 



Arts. Pages 

175-177 Pipe Sizes. Dripping- the Mains 265-267 

178 General Application of Steam System to Dis- 
trict 268-269 

References on District Heating 270 

CHAPTER XIV. (Temperature ContiTOl) 

179-182 General. Johnson, Powers and National Sys- 
tems 271-279 

CHAPTER XV. (Electrical Heating-) 

183-185 Discussion and Calculations 280-282 

CHAPTER XVI. (Refrigeration) 

186-187 Discussion of Systems 283-284 

188-189 Vacuum and Cold Air Systems 284 

190-191 Compression and Absorption Systems 285-288 

192 Condensers 289-291 

193 Evaporators 292-293 

194 Pipes, Valves and Fittings 294 

195-196 Absorption System 294-297 

197-198 Generators 298-299 

199-203 Condensers, Absorbers, Exchangeirs and 

Pumps 299-301 

204-205 Comparison of Systems 302 

206 Me.thods of Maintaining Low Temperatures 303-305 

207 Influence of Dew Point 305 

208 Pipe Line Refrigeration 306-307 

CHAPTER XVIL (Refrigeration, Cont'd) 

210-212 Calculations 308-312 

213-216 General Application 313-315 

217 Cost of Refrigeration 316-317 

References on Refrigeration 318 

CHAPTER XVIIL (Specifications) 

218 Suggestions on Planning Specifications 319-325 

APPENDIX. 

Tables and Diagrams 327 



CHAPTER I. 



HEAT — ITS XATURE, GEXERATIOX, USE, MEASUREMENT 
AND TRANSMISSION. 



1. Introductory: — In all localities where the atmosphere 
drops in temperature much below 60 degrees Fahrenheit, 
there is created a demand for the artificial heating of build- 
ings. As the buildings have grown in size and complexity 
of construction, so also this demand has grown in extent 
and preciseness, with the general result that from the 
antiquated open fire-place and" iron stove, there has devel- 
oped a science growing richer each day from inventive 
genius and manufacturing technique — the science of the 
Heating and Ventilating of Buildings. The purpose of this 
hand-book shall be to outline, concisely, the fundamental 
principles and practical applications of this science in its 
various branches. 

To the heating engineer of to-day, it may be that the 
exact nature of heat itself is of much less moment than 
its generation and transmission, but this fact should be 
impressed, — that heat is one form of energy, that it cannot 
be created except by conversion from some other form, and 
that it is infallibly obedient to certain physical laws and 
principles. 

In generating heat to-day for heating purposes, the 
almost universal method is combustion. The union of such 
substances as coal, wood or peat with the oxygen of the 
air is always attended by a liberation of heat derived fa*om 
the chemical action of the combination; and this heat is 
carried by some common carrier, such as air, water or 
steam, to the building or room to be heated where it is given 
off by the natural cooling process. In some instances this 
heat is converted into electrical energy, which is carried by 
wire to the place of use and given off by passing through a 
set of resistance coils, which convert it into heat; but this 
method is not much favored because of its inefficiency and 
the resulting expense. This latter objection would not hold 
in the case of water power installation, where the combus- 
tion of fuel is entirely eliminated. 



10 HEATING AND VENTILATION 

2. Measiireiiient of Heat: — In the measurement of heat, 
the most commonly accepted unit in practical engineering 
work is the British thermal unit, commonly abbreviated B. t. u., 
which may be defined as that amount of heat whicli will 
raise the temperature of one pound of pure water one de- 
gree Fahrenheit, at or near the temperature of maximum 
density, 39.1° F. (See also definition for Specific Heat). 
This unit value, the B. t. u., measures the quantity of heat, 
while the temperature measures the degree of heat. In 
equal masses of the same substance the two are propor- 
tional^ The Fahrenheit is the more commonly used tem- 
perature s-cale, especially in steam engineering. The unit of 
this scale is derived by dividing the distance on the ther- 
mometer between the freezing point and the boiling point 
of water into 180 equal degrees, the freezing point being 
marked 32°, and the boiling point 212°. All temperatures in 
this work will be taken according to the Fahrenheit scale, 
and all quantities of heat expressed in British thermal units. 

There is a second unit of quantity of heat considerably 
used, especially in scientific research, known as the calorie, 
commonly abbreviated cal., and defined as that amount of 
heat which will raise one kilogram of pure water one de- 
gree Centigrade, at or near the temperature of maximum 
density, 4° C. This Centigrade is a second temperature 
scale, the unit of which is derived by dividing the distance 
on the thermometer between the freezing point and the 
boiling point of water into 100 equal degrees, the freezing 
point being marked 0°, and the boiling point 100°. 

It is often found desirable to change the expression for 
temperature or for quantity of heat from one system of 
terms to that of the other. For this purpose the following 
formulas will be found useful: 

F=^C + S2 and C= {F-S2)f (1) 

where F = Fahrenheit degrees and C = Centigrade degrees. 
From these equations it may be seen that the two scales co- 
incide at but one point, — 40 degrees. For conversion of the 
quantity units the fullowing may be used: 

1 British thermal unit = 0.252 Calorie. 

1 Calorie = 3.9G8 British thermal units. 
These are for the aibsolute conversion of a certain quantity 
of heat from one system to the other. If, however, the 
effect of this heat is considered upon a given weight of sub- 



MEASUREMENT OF TEMPERATURE 



11 



Stai.ce and the weight also is expressed in the respective 
systems, the following- values hold: 

1 Calorie per kilogram =: i.s British thermal units per pound. 
1 I,:ritish thermal unit per pound = 0.555 Calorie per kilo- 
gram. 

Foir conversion tables from kilograms to pounds and vice 
ver^ - see Suplee's Mechanical Engineering Reference Book, 
foot 072, or Kent's Mechanical Engineers' Pocket-Book' 
hour 22. ' 

3. MeasTirement of High Teinperatnre.s:— For the meas- 
urement of temperatures up to the boiling point of mer- 





c. 




b. 



d. 



ig. 1. 



CTiry, or approximately 600'* F., the mercurial thermometer 
of proper range may be employed. It is more common, how- 
ever, to use some form of pyrometer for temperatures above 
500° F., as when the temperatures of stack gases or of fire 
box ga^es are desired. Pyrometers are built upon many dif- 



12 HEATING AND VENTILATION 

ferent principles, the graphite expansion stem type, shown 
in Fig. 1, a; the thermo-electric type, shown in Fig. 1, h; or 
the Siemens water calorimeter type, shown in Fig. 1, c. 
Various other methods might be mentioned, one of the t»'ist 
being temperature determination by the Seger cones, wllich, 
due to varying compositions, melt at different temperatnres. 
A line of these numbered cones is exposed to the swe'^^^'-f 
the gases to be measured, and their temperature deterr. heat, 
very closely by noting the number of the last cone w ^^ 
melts. The cones are numbered from 022 to 39 and indica 
temperatures from 590° to 1910" F., by approximate incre- 
ments of 20°. Fig. 1, d, shows cones 010, 09, 08 and 07, of 
which only the last is unaffected, and, from the table fur- 
nished with the cones, this indicates a temperature of 1000° F. 
4. Absolute Temperature: — In experiments that have 
been carried on with pure gases with the use of air ther- 
mometers, it has been found that air expands approximately 
-ri-Q of its volume per degree increa-se in temperature at 
zero F. or ^l-g- of its volume at zero C. From the same 
line of reasoning, by cooling the air below zero, the reverse 
process should be equally true, that is, for each degree 
Fahrenheit of cooling the volume at zero would be contract- 
ed -f-i-^. Evidently, then, if a volume of gas could be cooled 

4 o U 

to — 460° F., it would cease to exist. This theoretical point 
is called the absolute zero of temperature. All gases change 
to liquids or solids before this point is reached, however, and 
hence do not obey the law of contraction of gases at the very 
low temperatures. The fact that air at constant pressure 
changes its volume almost exactly in proportion to the abso- 
lute temperature, T, (460 + t] where t is temperature Fahren- 
heit) gives a starting point to be used as a basis for all air 
volume temperature calculations. For instance, if a volume 
of 20000 cubic feet be taken in at the air intake of a build- 
ing at 0°, and heated to 70°, its volume, by the heating, will 

become greater in the same proportion that its absolute teni- 
ae 530 

perature becomes greater; that is, = ; x = 23000 

20000 460 

cubic feet, or an increase of 15 per cent. 

Gage and Absolute Pressures. — Two common ways of ex- 
pressing pressures are in use. One is denoted by the expres- 
sion pressure by gage, and refers to the total pressure in a 
container minus the pressure of one atmosphere. Thus the 
expression "65 pounds boiler pressure, by gage" means that 



MECHANICAL EQUIVALENT OF HEAT 13 

the boiler is carrj'ing- 65 pounds pressure, per square inch of 
it'urface, above the pressure of the atmosphere, wliich is, for 
approximate calculations, taken at the standard pressure of 
14.696 pounds per square inch. Hence, the boiler carries 
within it a total pressure of 65 pounds plus 14.696 pounds or 
79.69t) pounds pel square inch. This total pressure is what 
is " ^wn as ahsoJute pressure, and when stated in pounds per 
foot o.fQ(^^ Q^ area, is called specific pressure. Like the volume 
hour, g^g^ so also the absolute pressure varies directly with 
^^^.bsolute temperature, other things being" constant. Hence 
.lie equation P F = R T, where P is the absolute pressure 
in pounds per square foot, V is the volume of one pound in 
cubic feet, T is the absolute temperature, and i? is a con- 
stant which for air is 53.22. From this equation, having 
given any two of the quantities, P, T or T, the third may be 
found. In very accurate calculations where the value 14.696 
is not considered close enough, the barometer may be read, 
and its readings, in inches of mercury, multiplied by the 
constant .49, to obtain the pressure of the atmosphere in 
pounds per square inch. 

Mechanical Equivalent of Heat. — By precise experiment, it 
has been determined that, if the heat energy represented by 
one B. t. u. be changed into mechanical energy without loss, 
it would accomplish 778 foot pounds of work. Similarly, 
one calorie is equivalent to 428 kilogrammeters. One horse- 
power of work is equivalent to the expenditure of 33000 foot 
pounds of work per minute. Hence one horse-power of 
work represents 42.416 B. t. u. per minute. 

Latent Heat. — Not all the heat applied to a body pro- 
duces change in temperature. Under certain conditions, the 
heat applied produces internal or molecular changes, and is 
called Intent heat. Thus if heat is applied to ice at the freez- 
ing point, no rise of temperature is noted until all the ice 
is melted; and again, heat applied to water at boiling point 
does not raise the temperature, but changes the water into 
steam. The first is called latent heat of fusion, and for 
ice is 142 B. t. u. per pound, while the latter is called latent 
heat of evaporation, and for water is 969.7 B. t. u. per pound. 
Specific Heat. — The ratio of the quantity of heat required 
to raise the temperature of a substance one degree, to that 
required to raise the temperatLire of the same weight of 
pure water one degree from the temperature of its maxi- 
mum density, 39.1 degrees, is commonly called the specific 
heat of the substance. The above is the accepted rule among 



14 HEATING AND VENTILATION 

physicists. This, however, has boon mcKiified by ongrineering 
pmctice so that the statement specific heat of icater is noi?^' 
understood to moan the average specific heat o£ vsMter X'^- 
tween 32 degrees and 212 degrees. (Amount of heii.t nec3,s- 
sary to raise one pound of water from 32 degrees F. to^ 212 
degrees F.) ^ ISO = 1 approximately. Table 24, Appendix, 
gives specific heats of substances. Seix^ 

5. Hadiutioii. Cimdiietiou and Convection: — The .^J heat, 
fiion of heat, next to its generation, forms an item ol-^ In 
interest to the heating engineer, for different forms of h^^ 
ing installations are based fundamentally on the differen.. 
ways in which heat is transmitted. These ways are usually 
quoted as being three in number — radiation, conduction and 
convection. 

Radiation. — This transmission of heat occurs as a wave 
motion in the ether of space, and is the way by which the 
heat of the sun reaches the earth. Heat of this form, usu- 
ally referred to as radiant heat, requires no matter for its 
conveyance, passes through some materials, notably rock- 
salt, without change or appreciaible loss, and travels, as does 
light, at the rate of 186000 miles per second. In the combus- 
tion of fuel the radiant heat given off to the surrounding 
metal from the rays of the fire is no doubt of much greater 
value than has ever been credited to it. We are indebted 
to the noted French physicist, L. Ser, who followed Peclet 
in his experiments in radiant heat in fire box boilers, for a 
very valuable amount of information. It is to be hoped 
that further experimentation may soon see the relation be- 
tween the "heat radiated from the incandescent surface of 
the fuel" and the "sensible heat in the escaping gases." 
This would be of great value to those engaged in the design 
and operation of boiler furnaces. 

CoxDrcTiov. — The second method of transmission is more 
commonly evident to the senses. If a rod of metal is heat- 
ed at one end, it is known that the heat is transferred, or 
conducted, along the rod until the other end becomes heated 
also. Conduction being, essentially, the way by which solids 
transfer heat, is hence of special significance in the calcu- 
lation of heat losses thrdugh the walls of a building. Rel- 
ative comluctivitij of a substance may be defined as the quantity 
of heat which passes through a unit thickness of the sub- 
stance in a unit of time across a unit of surface of the sub- 
stance, the difference of temperature between the two sides 
of the substance being one unit of the thermometric scale 



HEAT TRANSMISSION 



15 




Fig. 2. 



employed. Since the coimplexity of our building construc- 
tions renders it obviously impossibfe to reduce all losses to 
losses per unit thickness of the structure, we are not per- 
mitted to use the term "relative conductivity" but another 
term, i. e., "transmission constant," or rr/ic of transmiHHon. 
Thus Table IV, page 40, the rate of transmission K, given 
for a 6 inch studded frame wall, is .25 B. t. u. per square 
foot of surface per degree difference of temperature for one 
hour. It is readily seen that this table is the basis for the 
heat loss calculations of buildings. 

Convection. — Gases and liquids convey heat 
most readily by this method, which is funda- 
mental with hot air and hot water heating 
installations. If it is attempted to heat a 
body of water by applying heat to its upper 
surface, it will be found to warm up with 
extreme slowness. If, however, the source of 
heat be applied below the body of water as 
in Fig. 2, it will be found to heat rapidly, the 
water being distributed by circulating cur- 
rents having more or less force, and follow- 
ing, in general, the direction shown by the ar- 
rows. What actually happens is this: — water 
particles near the source of heat become lighter, 
volume for volume, than the colder particles 
near the top; then, because of the change in 
density, gravity causes an exchange of these 
particles, drawing the heavier to the bottom and 
allowing the heated and lighter particles to rise 
to the top, thus forming the circulation currents. 
This process is known as convection. It will 
never occur unless the medium expands con- 
siderably upon being heated, and unless the 
force of gravity is free to establish circulating 
currents. The hot water heating system may 
be considered merely as a body of water. Fig. 3, 
furnished with proper pipe circuits. When 
heated at one point, the water rises by convec- 
tion to the radiators, is there cooled, hence be- 
comes heavier, and descends by the return cir- 
cuit to the point of heat application, thus completing the 
circuit. The warm air furnace installation works similarly, 
air, however, being the heat-carrying medium. 




•M 



I 



n 



Fig. 3. 



CHAPTER II. 



AIR C03IP0SITI0N — VENTILATION HUMIDITY 



6. Composition of Atmospheric Air: — The subject of 
ventilation as applied to buildings would naturally be in- 
troduced by a brief consideration of the properties of the 
air supplied. This supply is a very important factor as re- 
gards both quality and quantity. In addition to its value 
as a heating- medium, it determines, in a large measure, the 
health of the occupants of the building. 

The human body may be considered as a well equipped 
and very complex power plant. As the carbon, hydro- 
gen and oxygen in the fuel and air supply in any mechan- 
ical power plant are consumed in the furnace, the resulting 
heat absorbed in the generating system and finally turned 
into work through the attached mechanisms, so the human 
body in a similar way, but at a much slower ,rate, absorbs 
the heat of combustion and turns it into work. The prod- 
ucts of combustion in both cases are largely carbon dioxide 
and water. The chief requisites of the mechanical plant 
are good fuel, good draft and good stoking. Similarly, the 
human body needs pure food, pure air and healthful exer- 
cise. Of the three, the second is probably of the greatest 
importance, since no person can keep in health with im- 
pure air, even though accompanied with the best of food 
and plenty of exercise. 

Air, to the average person, is made up of two elements, 
oxygen and nitrogen, in the volume ratio of about 20.9 to 
79.1 and a density ratio of about 23.1 to 76.9, respectively. 
We find in making a complete analysis of pure air, that a 
number of other elements and compounds enter into it, mak- 
ing a mechanical mixture which is somewhat complex. To 
the heating and ventilating engineer, however, two im- 
portant substances must be added to the two just stated, 
and a revision of the percentages will therefore be neces- 
sary. It may be said that pure air, as taken from the good 
open country and not contaminated with poisonous gases 
or the dust and refuse from the cities, would have about 



COMPOSITION OF AIR 17 

the following- composition. See Encyclopedia Britannica, 
Respiration. 

Oxygen Symbol O Per cent, of volume 20.26 

Nitrogen " N " " " 78.00 

Moisture ' " HoO '* '' " 1.7 

Carbon dioxide *' CO2 " " " .04 

These values are fairly constant, except that of the mois- 
ture, which may vary according to the humidity anywhere 
from + to 4 per cent, of the entire weight of the air. In 
places where the air is not pure, the following substances 
may be found in small quantities: carbon monoxide (CO), 
sulphuretted hydrogen (HoS), ozone, argon, compounds of 
ammonia, and compounds of nitric, nitrous, sulphuric and 
sulphurous acids. 

In the process of respiration, the lungs and the skin 
of the average person wall change the composition of the 
air film around the person from that given above to 
Oxygen Per cent, of volume 16 

Nitrogen " " " 75 

Moisture " " " 5 

Carbon dioxide ** " " 4 

Comparing these values with 'those for pure air, it will 
be seen that the oxygen has been reduced about one-fifth, 
the nitrogen has been reduced about one twenty-fifth, the 
vapor has increased three times and the carbon dioxide has 
increased one hundred times. Oxygen has been consumed 
in its uniting with the excess carbon and hydrogen in the 
System, and is given off as* carbon dioxide and water vapor. 
It may be seen from these ratios, that the very rapid increase 
in CO2 'and the accompanying imipurities of animal matter, 
would soon render unfit for use the air in almost any build- 
ing occupied by a number of people. To avoid this state of 
affairs, fresh air should be supplied continuously and at 
such points as will provide the most uniform circulation. 

7. Oxygen and Xitrogen: — The oxygen of the air fills 
about one-fifth of the volume in atmospheric air and is the 
element that makes combustion possible. The other four- 
fifths of the space might be said to be filled with nitrogen. 
In a providential way, this nitrogen acts as a sort of buffer 
in its mixture with the oxygen and serves to control the 
rapidi'ty with which the combustion takes place. Nitrogen 
seems to have little effect upon the respiration, except to 



18 HEATING AND VENTILATION 

retard the chemical action between the oxygen and carbon 
and the oxygen and hydrogen. If one were to attempt to 
live in an atmosphere of pure oxygen, the chemical action 
in the lungs would be so rapid that the human body would 
not be able to maintain it. 

8. Carbon Dioxide: — The amount of COo in the air is 
used as an index to the purity of the air. This is not con- 
sidered a poisonous gas. It has slight taste and odor but no 
color. It is found in many natural waters and manufac- 
tured beverages, the chief one being "soda water," which is 
made by forcing carbon dioxide into water under pressure. 
The real action of CO2 w.hen taken dnto the lungs is not 
well known. It has the effect of producing physical depres- 
sion, and where found in sufficient quantity would even cause 
death by suffocation, very similar to a submergence in 
water. Whatever its effect upon human life may be, its pres- 
ence in any room used for habitation is usually an indica- 
tion of the lack of oxygen and an excess of impurities thrown 
off by respiration. Pure air has four parts COo in 
10000 parts of air, and room air should never be 
allowed to have more than eight 'to ten parts in 10000 parts 
of air. It becomes the problem of the heating engineer, 
therefore, to provide air in sufficient quantities, and to enter 
and withdraw the air from the room in a manner such as 
will not be uncomfortable to the occupants, at the same 
time keeping the air fairly uniform in quality, throughout 
the room. Carbon dioxide in the exhaled breath is about 2.5 
times heavier than air of the same temperature, and there- 
fore would have a tendency to fall. It is exhaled, however, 
with excessive moisture and at a temperature higher -than 
that of the room air, both qualities giving it a tendency to 
rise. These latter factors probably neutralize the excessive 
density, and as long as the air is not absolutely quiet, would 
eventually result in a fair diffusion throughout the room 
air. In large audiences the heat given off fro-m the occu- 
pants is sufficient to cause strong air currents which, in 
rising, lift this impure air to the upper part of the room. 
In most systems the vitiated air is withdrawn from the 
room near the floor line. If, as is urged by some, the ven- 
tilating air enters near the floor line and is removed from 
the upper part of the room near the ceiling, the problem 
of heating the room will be more difficult and expensive. 



DETERMINING THE PURITY OP AIR ly 

The circulation of air within rooms is being given much at- 
tention now and it is hoped that some conclusive results 
may soon be obtained. There is no doubt that less air will 
be needed for proper ventilation if it is entered and removed 
in such a manner and from such parts of the room as will 
keep all the air within the room constantly niGving and yet 
free from localized air currents. 

A method of determining tJie pereentage of carhon dioxide in the 
air, based upo'n the fact that barium carbonate is nearly in- 
soluble in water, may be performed as follows: Provide 
eleven bottles with rubber stoppers having- two holes each, 
and connect them continuously by glass and rubber tubing, 
so that if suction be applied at the first bottle of the series, 
air will be drawn in at the last of the series and the same 
air will be passed through all. In this way a sample of the 
air to be tested may be drawn into each bottle. The capac- 
ities of the bottles must be made to be respectively, in 
ounces, 231/2, ISVa, leVs, 14, dVz, IVz, 5i^, 4, 3i^, 2i^ and 2. 
This may readily be done by partially filling with paraffine. 
Into each bottle is then placed V2 ounce of a 50 per cent, sat- 
urated solution of barium hydrate, Ba(OH)2. More of the 
air to be tested is drawn through the system until assurance 
is had that each bottle contains a fair sample. Each bottle is 
then thoroughly shaken, so that the liquid may be brought 
into good contact with the air sample. If the least turbidity 
or cloudiness appears in the 

First or largest bottle indicates 0.04 per cent. CO2 

Second bottle indicates 0.06 " " " 

Third " " 0.07 " 

Fourth " " 0.08 *' 

Fifth " " 0.10 " 

Sixth " " 0.15 " 

Seventh " " 0.20 " 

Eighth " " 0.30 " 

Ninth " " 0.40 " 

Tenth " " 0.60 '' 

Eleventh " " 0.90 " 

Care must be taken to have a fair sample of the air in 
each bottle. The glass tubes through the rubber stoppers 
should extend no farther than the bottom of the stoppers. 
Fig. 4, a, shows four of the bottles and their connections. 



20 



HEATING AND VENTILATION 



As an example, suppose that the air of a room was tested 
and that in the first, second, third, fourth, fifth and sixth 
bottles the liquid became turbid after vigorous shaking. 
Such room air would have contained 0.15 per cent, of carbon 
dioxide, and would have been considered quite unfit for 
breathing. 





^ 



trrr^ 



^^=r-^ W^ 4^^' tr^ 




Fig. 4. 



A second, less cumbersome, and more delicate method of testing 
for the percentage of carbon dioxide will be described, as it 
is the method commonly used and only requires compara- 
tively simple apparatus, as shown in Fig. 4, b. A bottle of 
about 6 ounces capacity is fitted with a rubber stopper hav- 
ing two holes. Through one hole a glass tube is brought 
from the bottom of the bottle, and to the outer end of the 
tube is connected a valved bulb similar to those found on 
atomizers. Into the bottle are placed 10 cubic centimeters 
of a solution made by dissolving .53 grams of anhydrous 
sodium carbonate, Na2 CO3, in 5 liters of water, and adding 
.01 gram of phenolphthalein. The water used must have been 
previously boiled for at least one hour in an open vessel. 
With the apparatus so prepared, squeeze the bulb, thus forc- 
ing air from the room thTOugh the liquid and into the bot- 
tle. The open hole in the rubber stopper is then closed with 
the thumb, and the bottle shaken for twenty seconds, 
then another bul'b-full of air is inserted, and again shaken. 
This process is continued and the number of bulbs of air 
noted until the red color of the solution, due to the phenolph- 
thalein, disappears. This number of bulb fillings is indica- 
tive of the purity of the air according to the table below. 
After such an apparatus is completed, it must be calibrated 



DETERMINING THE PURITY OP AIR 21 

before being- used. This is done by testing the number of 
bulb fillings of pure country air necessary to clear the 
liquid, which will usually vary from 40 to 70. A new table 
for that special apparatus is then obtained from the one 
given below by proportion. In the table given, this number 
of bulb fillings, with purest country air, is 48. If, with the 
apparatus made up, it is found that, say, 60 bulb fillings are 
required, then the proportionate table would be made by 
multiplying the number of bulb fillings given below by the 
ratio of 60 -^ 48, or 5 to 4. It is important that the bulb be 
compressed the same amount for each filling, and that the 
shaking of the bottle and contents be continued the same 
length of time after each filling, to obtain uniform results. 







TABLE 


I. 






Fillings 


Per Cent. 


CO2 


Fillings 


Per Cent. COo 


48 


.030 






15 


.074 


40 


.038 






14 


.077 


35 


.042 






13 


.08 


30 


.048 






12 


.083 


28 


.049 






11 


.087 


26 


.051 






10 


.09 


24 


.054 






9 


.10 


22 


.058 






8 


.115 


20 


.062 






7 


.135 


19 


.064 






6 


.155 


IS 


.066 






5 


.18 


17 


.069 






4 


.21 


16 


.071 






3 


.25 



The methods outlined for the approximate estimation of 
COo are satisfactory for determining whether or not ventila- 
ting systems maintain a proper degree of purity of air. If 
exact percentages of CO, CO2, O and N are required, the Orsat 
apparatus must be employed, for description of which see 
Engineering Chemistry by Stillman, page 238. See also Car- 
penter, H. & V. B., Chap. II, and Hempel's Gas Analysis, 
translated by Dennis. 

9. Amount of Air Required per Person: — The need of a 
continuous supply of fresh air in our residences and business 
houses can scarcely be over-estimated. Health is probably 



22 HEATING AND VENTILATION 

the greates't of all blessings and pure air is absolutely es- 
sential to health. The average adult, when engaged in or- 
dinary indoor occupations, will exhale about twenty cubic 
inches of air per respiration. He will also have sixteen to 
twenty respirations per minute, making a total of 400 cubic 
inches or, say, .25 cubic foot of air exhaled per minute. If 
as in Art. 6, exhaled air contains 4 per cent. COo, then 
the average person will exhale 60 X .25 X .04 = .6 cubic foot 
COo per hour, (Pettenkofer, Smith & Parker), which is con- 
stantly being diffused throughout the air of the room, thus 
rendering it unfit for use. If the carbon dioxide and the 
other impurities could be disassociated from the rest of the 
air and expelled from the room without taking large quan- 
tities of otherwise pure air with it, the problems of the heat- 
ing engineer would be simplified, but this cannot be done. 
Because of this rapid diffusion, it is necessary to flood the 
room with fresh air in order that the purity may be main- 
tained at a safe value. The ideal conditions would be to 
have it the same as that of the outside air, but the mechan- 
ical difficulties around such a ventilating system would be so 
great as to render it prohibitive. The standard of purity 
which should be aimed at, and one, as well, which may be 
attained with a first class system, is, .06 of one per cent. 
CO2, i. e., six parts of COo in 10000 parts of air. A system, 
however, which maintains a standard of 8 parts in 10000 
would be considered fairly satisfactory. This may be put in 
a simple form for calculation. 

Let Qi = cubic feet of atmospheric air needed per hour 
per person; A = cubic feet of CO2 given off per hour per 
person; n = .the standard of purity to be maintained (al- 
lowable parts of COo in 10000 parts of air); and p = the 
standard of purity in atmospheric air, say, 4; then 

If we wish to maintain a purity in the room of seven 
parts CO2 in 10000 parts of air, and pure air contains four 
parts in 10000, we have Qi = .6 -^ (.0007 — .0004) = 2000 
cubic feet of air per hour. 

Another formula, quoted from Carpenter's Heating and 
Ventilating of Buildings, very similar to the above, is 

ah 
Oi = ^ (3) 



AIR REQUIRED PER PERSON 



23 



where a = the purity of the exhaled breath, say 400 parts 
in 10000, n = the purity to be maintained in the room and 
& = the cubic feet of air exhaled per minute. Substituting, 
as above, 

Qi - (400 X 60 X .25) H- (7 -— 4) = 2000 cubic feet. 

Based upon .6 cubic foot of COo exhaled per person per 
hour, Table II gives the amount of air needed to maintain 
the various standards of purity. 

It should be understood that no hard and fast rule can 
be given for the air requirement per person. This, natur- 
ally, would be a different amount when considering the 
physical development for each person in health; it would 
also be different for the same person according to his occu- 
pation at the time, sleep being the least, waking rest some- 
what greater, and physical exercise the greatest; but it 
varies decidedly with the state of the person's health, or the 
sanitary value of his surroundings. According as the degree 
of purity is demanded, the air supply must be increased to 
suit it. 

TABLE II. 
Cubic Feet of Air per Person per Hour. 



n 


A 


Qi 




6 


.6 


3000 




7 


.6 


2000 




8 


.6 


1500 




9 


.6 


1200 




10 


.6 


1000 





Generally, it is understood that Uie average adult sub- 
jected to average conditions will require 1800 cubic feet of air 
per hour. The amount of air needed for ventilation then in 
most cases can be represented by the formula Q' = 1800 N, 
where N — the number of people to be provided for. 

The following table quoted from Carpenter's H. & V.- B., 
and from Morin in Encyclopedia Britannica, gives a fair 
value for the amount of air per occupant per hour, that 
should be supplied to rooms used for yarious purposes. 



24 HEATING AND VENTILATION 

TABLE IIL 

Hospitals, ordinary 2000-2400 cu. ft. per hour 

epidemic 5000 " " " 

Workshops, ordinary 2000 " ** " 

unhealthy trades 3500 " " 

Prisons 1700 " " " 

Theaters 1400-1700 " " " 

Meeting halls 1000-2000 * 

Schools, per child 400- 500 " " " 

•* adult 800-1000 " " " 



Recent practice would tend to increase these values 
somewhat; especially those relating to school house ventil- 
ation, where a good estimate would be 800 to 1800 respec- 
tively. 

One ordinary gas burner of 20 candle power, using four 
cubic feet of gas per hour, will vitiate as much air as three 
or four people. Where many lamps are used, this fact 
should be taken into account. 

In summing up ilic suhject of fresh air supply, it is well to call 
attention to the fact that the ordinary running conditions of 
any room cannot be absolutely determined by a single test 
for carbon dioxide. Trials should be frequently made and 
records kept. Upon one day the conditions may be unusually 
favorable and would show a small -amount of COo even 
though a very small amount of fresh air be admitted; while 
on other days, when the conditions are not s-o favorable, a 
large amount of fresh air would have to be supplied to main- 
tain the proper purity within. If the only requirement, 
therefore, governing the ventilation of buildings should be 
that a satisfactory COo test be passed, there would be a large 
opportunity to overrate or underrate, as the case may be, 
the ventilating system of the building. The only safe method 
in rating ventilating systems is to require a minimum air supply 
in addition to a maximum permissible percentage of CO2. 

The purification of air hy o.zoni::ing if has recently been advo- 
cated and by some it is claimed to be the real solution of 
the bad air problem. Definite scientific data are still lack- 
ing upon which to base any authoritative sitatements, al- 
though the invigorating effects of breathing ozonized air 
will be testified to by many. Ozone is an unstable form of 



MEASUREMENT OP HUMIDITY 25 

oxygen, probably containing- a greater number of atoms per 
molecule, and is formed by passing air through a liighly 
charged electric field. Because of its unstability as a sub- 
stance it readily breaks up and becomes more active as an 
oxidizing agent than oxygen itself. In its decomposition a 
part goes into combination with substances in the air, such 
as carbon impurities thrown off from the human body, and 
burns them up, leaving the balance which is probably pure 
oxygen. If in the future the purifying effects of ozone are 
found to substantiate the claims made by some, ventilation 
problems may thus be readily solved by air washing and 
ozonizing. 

10. 3Ioistnre with Air: — Moisture with the air is a bene- 
fit to both the heating and ventilating systems in any room. 
T\nith moisture in the room, a person may feel comfortable 
when the temperature is several degrees lower than the 
comfortable temperature of dry air. Dry air takes up the 
moisture from the skin. The vaporization of this moisture 
causes a loss of heat from the body, and gives to the per- 
son a sense of cold, which is only relieved when the tem- 
perature of the room is increased. Air space that is fairly 
saturated with moisture will not permit of much evaporation 
from the skin, because there is not much demand for this 
moisture with the air; consequently the body retains that 
heat and the person has a sensation of warmth which is 
only relieved by lowering the temperature of the air of the 
room. On the other hand, at low temperatures the mois- 
ture with air chills the surface of the skin by convection, 
a condition that is not so noticeable when the air is dry. 
It follows from the above statement that the range of com- 
fortable temperatures is less for moist air than for dry air. 

Concerning the effect of moisture in its relation to the 
heating and ventilating of the room, we may say that thor- 
oughly dry air has not the quality of intercepting radiant 
heat; moisture, however, has this quality. Moist air has 
also somewhat less weight than dry air and is more buoyant. 
Because of the possibility of storing up the radiant heat 
within the particles of moisture, and, because of its con- 
vection qualities, it serves as a good heat carrier for the 
heating system. 

11. Humidity of the Air: — The actual humidify is the 
amount of moisture, expressed in grains or in pounds per 



26 



HEATING AND VENTILATION 



cubic foot, mixed with the air at any temperature. The 
relative humidity is the ratio of the amount of moisture actu- 
ally with the air divided by the amount of moisture which 
the same volume could hold at the same temperature when 
saturated. It is very important that the heating engineer 
be able to add to or to take away from the amount of the 
moisture in the air supply of any building. To find the 
amount of moisture that should be added or subtracted in 
any case, it is first necessary to determine the humidity of 
the air current at various points along its course. This 
may be obtained by the aid of the wet and dry bulb ther- 
mometer or by any one of a number 
of hygrometers supplied by the 
trade. The wet and dry bulb ther- 
mometer has a very simple appli- 
cation, and is probably in most gen- 
eral use. The principle of its ap- 
plication is as follows: having two 
thermometers, Fig. 5, let one of 
them register the temperature of 
the room air, the other one being 
kept wet by a cloth which covers 
the bulb and projects into a vessel 
filled with water, shown between 
the two thermometers. If the air 
is saturated the two thermometers 
will record the same temperature; 
if, however, the air is not saturated 
the thermometer readings will dif- 
fer an amount depending upon the 
humidity. It will readily be seen that 
the lowering of the mercury in 
the wet thermometer is due to the extraction of the heat 
in vaporizing the moisture from the bulb to the air. 

In taking readings, let the mercury find a constant level 
in each thermometer and then note the difference in tem- 
perature between the two. In Table 11, Appendix, at this 
difference and at the room temperature read off the rela- 
tive humidity; then take from Table 12, Appendix, the 
amount of moisture with saturated air at the temperature 
recorded by the dry thermometer, and multiply this by the 
humidity. The result is the amount of moisture with the 
air per cubic foot of volume. 




Fig. 5. 



MEASUREMENT OF HUMIDITY 



27 



Application. — Pwooni air, 70 degrees; difference in readings, 
6 degrees. From Table 11, the humidity is 72 per cent. 
From Table 12, col. 7, .72 X .001153 = .00083 pounds per 
cubic foot. 

To avoid the necessity for the use of tables, various in- 
struments have been designed, which, graphically, give the 
relative humidity directly. Pig. 6 shaws such an instrument, 



#^ 



m 



^ci 



%^M 


if,z / ^^^, V -^^H^ 


^SK 


/ - "^"^ 


— "^=— 


"^^ 


I'll. 




— znjr 



Fig. 6. 



commonly known as the hygrodeik. To find, by it, the relative 
humidity in the atmosphere, swing the index hand to the 
left of the chart, and adjust the sliding pointer to that de- 
gree of the wet bulb thermometer ^scale at which the mer- 
cury stands. Then swing the index hand to the right until 
the sliding pointer intersects the curved line which extends 
downward to the left from the degree of the dry bulb 
thermometer scale, indicated by the top of the mercury 
column in the dry bulb tube. At that intersection, the in- 
dex hand will point to the relative humidity on scale at bot- 
tom of chart. Should the temperature indicated by the wet 
bulb thermometer be 60 degrees and that of the dry bulb 
70 degrees, the index hand will indicate humidity of 55 



28 HEATING AND VENTILATION 

per cent., when the pointer rests on the intersecting line 
of 60 degrees and 70 degrees. 

For accurate work any instrument of the wet and dry hulb type 
should be used in a current of air of not less than 15 feet per second. 

Note. — A very elaborate series of experiments conduct- 
ed by Mr. Willis H. Carrier of Buffalo, New York, and pre- 
sented as a paper before the American Society of Mechan- 
ical Engineers in 1911, seems to show a theoretical humidity 
under varying conditions of temperature somewhat different 
from that obtained by the U. S. Weather Bureau, which has 
always been considered as a standard. Tables 11 and 12, 
Appendix, are used as reference in this book but Fig. A fol- 
lowing Table 13, shows the variation between the results 
obtained by Mr. Carrier and those obtained by the Govern- 
ment. The two charts Fig. B and Fig. C in addition to Fig. 
A are extracted from Mr. Carrier's work with his permis- 
sion. The com'pleteneiss with which this data has been 
worked up permits almost any information desired to be 
obtained from these two charts. 

12. For Close Approximations and to avoid calculations, 
the humidity chart, Fig. 7, may also be used in determining 
relative humidity, absolute humidity, dew point, temperature 
of wet bulb and temperature of dry bulb. On the left of the 
chart is a scale referring to horizontal lines giving tempera- 
tures of the wet bulb. The scale on the right hand, referring 
to the lines curving downward from right to left, is the scale 
of the room, or dry bulb, temperatures. The scale along the 
bottom of the chart is one of relative humidity. The scale of 
numbers up the center of the chart refers to the lines curving 
downward from left to right, and indicates the absolute hu- 
midity, i. e., grains of moisture per cubic foot with the air. 
The use of the chart may be most readily understood by a 
few applications. 

Application. — Given dry bulb 70 degrees and wet bulb 60 
degrees. Determine relative humidity, absolute humidity, 
temperature of dew point for room, etc. First, starting on 
the right hand scale at 70, follow down the line this number 
refers to until it crosses the horizontal line of 60 degrees, 
wet bulb temperature. From this intersection drop to the 
relative humidity scale and read there 55 per cent. This may 
be checked with the table. To obtain the absolute humidity 
it will be noticed that the intersection of the 70 degree and 



MEASUREMENT OF HUMIDITY 



29 



HYGROMETRIC CHART 



GIVING 

HYGROMETER TEMPERATURES. RELATIVE HUMIDITY GRAINS OF MOISTURE PER CU 




10 20 30 40 50 60 70 80 • 90 100 

RELATIVE HUMIDITY IN ^'ER CENT.. 

Fig. 7. 



NOTE. — Fig. 7 represents two charts in one. First: the dry bulb 
temperature curve, which drops to the left, unites with the wet bulb 
and relative humidity coordinates. Second: the absolute humidity 
curve, which rises to the left, unites with the dry bulb and relative 
humidity coordinates. This makes it possible to use the two charts as 
one, through the relative humidity scale which is common to both. 



30 HEATING AND VENTILATION 

55 per cent, coordinates shows 4.4 grains per cubic foot. If the 
room should cool, the absolute humidity would remain the 
same until the dew point is reached (neglecting air contrac- 
tion), hence, following down the 4.4 grain line to 100 per cent, 
gives the room temperature as 52 degrees, showing that if so 
cooled the air would begin depositing moisture at this tem- 
perature. Again if the room should heat to 90 degrees, the 
relative humidity may be obtained by following the 4.4 
grain line to its intersection with the 90 degree coordinate 
line of room temperature, and from this intersection dropping 
to the relative humidity scale, reading there 31 per cent. 
Thus, having given air under any set of conditions, the 
effect that a change in any one of these would have upon 
the remaining may be obtained without calculations. 

13. The Theoretical Amount of 3Ioistiire to be Added to 
Air so as to 3Iaintain a Certain Humidity: — 'Warm air has a 
much greater capacity for holding moisture than cold air. 
According to the law of Gay-Lussac, when air is taken 
at a given outside temperature and heated for interior 
service, the volume increases with the absolute tempera- 
ture. See Art. 4. On the other hand the humidity de- 
creases rapidlj'. Air thus treated becomes dry and unpleas- 
ant to the occupants, as well as being detrimental to the 
furnishings of the room. Some means should, therefore, be 
provided to supply this moisture to the air current. 

In calculating the amount to be added, let Q == volume 
of aiir in cubic feet per hour entering the room at the reg- 
ister; t = its temperature in degrees and T = (460 + f) = 
its absolute temperature; let Q' and Qo = the correspond- 
ing volumes after entering and before entering, with 
t' and to the temperatures in degrees, and 7" = (460 + t') 
and To = (460 + to) the absolute temperatures; also, let u' 
and uo be the humidities, respectively, of the room air and 
the outside aiir. Then, from the equations 

TQ' — TQ and TQo - ToQ (4) 

find Q' and Qo. 

From Table 10 or 12, Appendix, find the amounts of mois- 
ture If' and Mo in one cubic foot of saturated air at the tem- 
peratures f and to\ multiply these by the respective humidi- 
ties and volumes, and the difference between the two final 
quantities will be the amount of moisture required per hour 
as expressed by the formula 

W — Q'M'u' — QoMoUo (5) 



MEASUREMENT OP AIR VEr^OCITIES 



31 



4.- 



Application. — Let Q = 5000, t = 130, f = 70, U = 30, u' = .50, 
uo =r .50, M' = 7.98, and Mo — 1.935, then 

Q' = 5000 X 530 -^ 590 = 4490 

Qo = 5000 X 490 -^ 590 = 4154 

W = 13896 grains, or 1.983 pounds per hour. 
This means that approximately 2 pounds of water would be 
evaporated for every 5000 cubic feet of fresh air entering 
the register under the above conditions. 

14. Velocity in tlie Convection of Air "by the Applica- 
tion of Heat: — Let ho Fig-. 8, be the height of the chimney 
or stack. If the temperature of the gases 
within the chimney G D he the same as that 
of the entering air, then there will be na 
natural circulation, because the column C D, 
will just balance a corresponding column 
A B upon the outside; but if the temperature 
of the chimney gases C D and entering air 
A B he tc degrees and to degrees, respectively, 
the chimney gases being (tc — to) degrees 
greater than that of the outside air, then, 
upon entering the chimney, the gases will 
become less dense and expand an amount 
proportional to the absolute temperature. 
With an outside column of 7io feet in height, 
it will then require a column within, Jio + he 
feet in height to produce equilibrium; in oth- 
er words, the column of gas producing mo- 
tion in the chimney has a height of he feet. 
Assume, in the system of A B C D E, that the 
cross sections at all points be uniform, then the volumes of 
A B (imaginary column) and C E (actual column) are to 
each 'Other as their respective heights, i. e., 
Yo :Yo-\-Vc : : ho : ho -f he, or ho : 460 + #o : : ho + he : 460 + tc 
Prom this we obtain he (460 + to) = ho (tc — to) and 

7?o (tc — to) 



B 





—3 
> 


f 

y 




to 


K 


o 


u 









Fig. 8. 



460 + to 



(6) 



Substituting for h in the equation v = \/2 gh, its correspond- 
ing value he, we have 



V = V2ghc — 8.02 ; /<o (tr — to) 



(7) 

460 -h to 

It is found in practice that the theoretical velocity as 
given by this formula is never obtained, because of the 



32 



HEATING AND VENTILATION 



friction of the sides of the chimney and other causes. Mr. 
Alfred R. Wolff quoted the actual discharge from the chim- 
ney as 50 per cent, of the theoretical. This estimate may 
be fairly correct for chimneys of the larger sizes, but may 
not be realized on the smaller ones used in residences. As 
the transverse area becomes smaller, the percentage of fric- 
tion increases very rapidly and soon becomes the principal 
factor. Prof. Kent assumes a layer of gas two inches thick 
next the interior surface as being ineffective. This, if ap- 
plied to small cross-sectional areas, increases the size of 
the chimney rapidly from the calculated amount. 

When formula 7 is applied to hot air stacks in the 
heating systems, the friction is much less because of the 
smooth interior, and the actual velocity of the air should 
reach 60 to 70 per cent, of the theoretical. 

15. Measiirement of Air Velocities: — See also Arts. 123- 
125. In ventilating work it is often of the greatest impor- 
tance to determine air velocities accurately. The correct de- 
termination of the sizes of air propelling fans or blowers 
depends upon the ability to accurately measure the velocity 
of delivery. In acceptance and other tests this measurement 
is equally important. However, no entirely satisfactory and 
trustworthy method of obta/ining this measurement has as 
yet been devised. 

The velocity of moving air is most commonly measured 
by means of a vane wheel instrument called the anemometer. 
It consists essentially of a delicately pivoted wheel holding 
from 6 to 15 vanes and similar to the common wind-mill 

To the shaft is connected a recording 
mechanism of some sort, the simplest 
being merely dials which show the 
velocity of the air traveling past the 
instrument, by the reading of which 
against a stop-watch, the speed per 
unit of time may be obtained. Since 
the instrument works against the 
friction of m.oviing parts, its readings 
are subject to serious variation, and 
even with frequent calibration, it is 
not to be relied upon where results 
are required accurate to within 20 
per cent. Various tests of anemom- 
Fdg. 9. eters by comparison to the absolute 



wheel. See Fig. 9. 




PITOT TUBE 



33 



reading's of a gas tank have shown errors as high as 35 
per cent, slow, to 14 per cent, fast, with the discharge from 
pipes 8 inclies to 24 inches in diameter. Hence, in general, 
it is very safe to say that the anemometer as an instrument 
for velocity measureiment in precise w^ork should be used 
with great care. 

A second method of velocity measurement, and one 
applying as readily to liquids as to gases, is that of using 
the Pitot tube principle. Whenever, in a liquid or gas, a 
pressure produces a flow, part of this pressure, usually 
termed the velocity head, is considered as transformed into 
velocity; while a second part, usually called the pressure 
head, acts to produce pressure in the fluid. If now, as at 
A, in Fig. 10, a tube be inserted into a pipe carrying a 




Fig. 10. 



current of air or other moving fluid, and the end of this 
tube be bent so the plane of the opening is perpendicular 
to the direction of the flow, a pressure in the tube will 
result, due to both the velocity head and the pressure head; 
and the difference in levels in the connected manometer 
tube will indicate this sum of pressures in terms of inches 
of water or mercury. If, hov/ever, a tube be inserted as at 
B, with the plane of its opening parallel to the direction 
of the flow, a pressure in the tube will result, due only 
to the pressure head in the moving fluid; and the difference 
in levels in the connected mano^meter tube will indicate this 
pressure only. Then, by subtraction of the two manom- 
eter readings, the velocity head only is obtained, expressed 
in inches of water or mercury, whichever the manometer 
may contain. 

At C is shown the instrument as commonly applied, 
with both tubes together and connected one to either leg 
of the manometer tube so that the subtraction is automatic 



34 



HEATING AND VENTILATION 



and the difference in levels read is caused by the velocity 

only. Having-, then, the head of pressure due to velocity, 

to find the actual velocity apply the formula r = V2gh where 

V = velocity in feet per second, g = acceleration of g^ravity 

in feet per second, per second, and h = the velocity head of 

the air in feet. If the manometer contains water, then, 

at 60 degrees, the ratio between the specific gravity of air 

62.37 

and water is = 816.4. See Tables 12 and 8, Appendix. 

.0764 

Hence the above formula may be reduced to the more read- 
ily available form of 



.=V 



2 X 32.16 X 816.4 X 



or 



12 



66.2 V /i. 



(8) 



where hw = the difference in height in inches of the columns 
of a water manometer, with both legs connected as described, 
and a temperature of 60 degrees. By a similar method the 
formula may be reduced for a mercury or other manometer, 
or for other temperatures than 60 degrees. (See Art. 1021, 
Trans. A.'S. M. E. Vol. XXV.) 

In using the Pitot tube or the anemometer, the fact 
should not be lost sight of that the velocity varies from 
a minimum at the inner walls of the tube to the maximum 
at the center of the tube. It seems that the friction at the 
inner walls throws the moving fluid into a number of 
concentric layers, those toward the center moving the fast- 
est, those toward the inner wall of the pipe the slowest. 
With a circular tube, the variation of velocities of these 
different layers may be approximately represented by the 
abscissae of a parabola, Fig. 11, with its axis on the axis of 
the circular pipe. AVcisbach, on page 189 of his Mechanics of 





Fig. 11. 



CHIMNEYS 35 

Air Machinery, quotes the average speed at two-thirds of the 
radius from the center, this value being obtained by ex- 
periments. For conduits of other shapes the position of 
mean velocity must be determined experimentally. This 
variation of velocity from the center of the stream less- 
ening" toward the walls may possibly account for the varia- 
tions shown by the anemometers. It is evident that 
if such an instrument, with a given diameter of vane 
wheel, be placed at the center of a pipe of large radius it 
would tend to register a higher velocity than the average. 
Automatic recording meters may be obtained for keep- 
ing permanent records of the flow of air and steam through 
pipes and ducts. The record from the meter indicates direct- 
ly the cubic feet of free air or other fluid used during each 
hour of the day. 

16. Amount of Air Heqnired to Burn Carbon: — The chief 
product in the combustion of carbon with the oxygen of the 
air is CO2. The atomic weight of carbon is 12 and that 
of oxygen is 16, hence the chemical union of the two form- 
ing CO2 is in the proportion of carbon 12 and oxygen 32 
or as 1 : 2.66. For each pound of carbon consumed, 2.66 
pounds of oxygen will be needed and the product will weigh 
3.66 pounds. If pure air contains 23 per cent, oxygen, then 
one pound of carbon will need 2.66 -4- .23 = 11.7, say 12 
pounds of air for complete combustion. One cubic foot 
of air at 32 degrees weighs .0807 pounds, then 12 -^ .0807 = 
148 cubic feet of air necessary to burn one pound of car- 
bon if all the oxygen of the air is burned. With volumes 
proportional to the absolute temperatures, this air at 70 
degrees would be 160 cubic feet; at 200 degrees, 200 cubic 
feet; at '400 degrees, 260 cubic feet; and at 600 degrees, 320 
cubic feet. 

17. Probable Amount of Air Used: — It seems reason- 
able to assume, however, that in practice from two to three 
times as much air goes through a furnace as would be 
needed for perfect combustion. Taking this at 2.5, then the 
cubic feet of air found from the above would be approxi- 
mately; 32 degrees, 370 cubic feet; 70 degrees, 400 cubic 
feet; 200 degrees, 500 cubic feet; 400 degrees, 650 cubic feet; 
and 600 degrees, 800 cubic feet. 

18. To Determine the Transverse Area of a Chimney 
for Any Given Heigrht: — Substitute ho and the assumed 



36 HEATING AND VENTILATION 

values of tc and to in formula 7, Art. 14. From this find 
the velocity of the chimney gases, and divide the total 
volume of air used in any given time, Art. 17, by the corre- 
sponding velocity. 

19. Application to tlie Chimney of a lO-Room Resi- 
dence: — Given: total heat loss from the building per hour, 
10000 B. t. u.; coal, 13500 B. t. u. per pound; furnace 
efficiency, 60 per cent.; temperature at bottom of chimney, 
200 degrees F. ; height of chimney, 30 feet above the grate; 
average temperature of chimney gases, 150 degrees. (The 
greatest difficulty is experienced when the fire is first 
started before the chimney is warmed up. The temperature 
of the stack gases at such a time is very low.) Take the 
outside air temoDerature, 40 degrees F., and find the size of 
the chimney. 

A heat loss of 100000 B. t. u. per hour will require 
100000 -^ (13500 X .60) =: 12.4 pounds of coal per hour at 
the grate; -then w-ith a temperature of 200 degrees at the 
bottom of the chimney, this will need to pass 500 X 12.4 = 
6200 cubic feet of air per hour. The velocity of the chim- 
ney gases, according to formula, is 20.5 feet per second or 
73800 feet per hour. Assuming the real velocity to be 
25 per cent, of this amount, "we have approximately 18450 
feet per hour; then the net sectional area is 6200 -^ 18450 
= .34 square foot or 49 square inches. To fit the brick 
work this would probably be made 8 inches X 8 inches. 

20. All Chimneys should have a Smooth Finish on the 
Inside: — -Probably the best arrangement that can be made 
is to build the chimney of hard burned brick around hard 
burned tiles of suitable internal size. These tiles can be 
had of outside sizes such that they can easily be made to 
work in with the brick work. Table 15, Appendix, shows 
chimney capacities that will be safe in average practice. 
Flues should preferably be made round in section, as this 
form presents less friction to the gases than any other. 
Flues should never be built less than ten inches in diam- 
eter, or eight by ten inches rectangular. The value of a 
flue depends very much upon the volume of passage due 
to area, and velocity due to height. Velocity alone is no 
proof of good draft for there must also be sufficient area 
to carry the smoke. The top of a chimney with reference 



CHIMNEYS 37 

to its position relative to neighboring structures is a very 
important consideration. If the top is below any nearby 
portion of the building", eddy currents tending to enter the 
top of the flue may be formed and seriously reduce the draft. 
Under such conditions a shifting cowl, which always turns 
the outlet away from adverse currents, may be advisable. 
Good draft is very essential to the success of any type of 
heating system, and the purchaser of a furnace or heater 
should be required to guarantee sufficient draft before a 
maker is expected to guarantee a stated rating of his 
furnace or heater. 



38 HEATING AND VENTILATION 



REFERENCES. 

References on Ventilation and the Air Supply 

Technical Books. 

Moore, Tlic School House, p. 2 4. Monroe, Steam Heat, d Tent., 
p. 99. Carpenter, Heat, d Tent. Bldgs., p. 21. Hubbard, Power, 
Heat. cC- Tent., p. 408. Allen, Xotes on Heat. & Tent., p. 91. 
Ency. Brit., Vol. XXIV, p. 157, also Vol. XX, p. 474. 

Technical Periodicals. 

Engr. Rev., Sanitation and Ventilation in Boston School 
Houses, W. B. Snow, March 1908, p. 15, Subway Ventilation, 
J. B. Holbrook, Jan. 1905, p. 18. Ventilation of School Rooms, 
Nov. 19^05, p. 6. Heat. cC- Tent. Magazine. A Scotchman's Notes on 
Ventilation, Alex. Mackenzie, May 1906, p. 15. Air Analysis as 
an Aid to the Ventilating- Engineer, J. R. Preston, Oct. 1906, 
p. 11. Domestic Engineering. Ventilation in its Relation to Health 
W. G. Snow, Vol. 52, No. 4, July 23, 1910, p. 102; Vol. 52. No. 
6, Aug-. 6, 1910, p. 154. Ventilation of Isolated Offices, C. L. 
Hubbard, Vol. 45, No. 10, Dec. 5, 1908, p. 274. Humidity, 
Its Necessity and Benefits, W. W. Brand, July 1910. 
The Permanent Plac^ of the Air Wvasher in Heating" 
and Ventilating Work, Feb. 1910. Trans. A. S. H 
& T. E. The Necessity of Moisture in Heated Houses, R. C. 
Carpenter, Vol. X, p. 129. Need of Ventilation in Heated 
Buildings, Vol. X, p. 183. Changing the Air in a Building, 
Vol. X, p. 285. Effect of Humidity on Heating Systems, Vol. 
IX, p. 323. Necessity of Ventilation, H. Eisert, Vol. V, p. 57. 
The Engineering Magazine. Humidifiers, — Their Principles and 
Useful Applications, S. H. Bunnell, June 1910. The Heating, 
Ventilating and Air Conditions of Factories, P. R. Moses, 
Aug. and Sept. 1910. Engineering Record. Ventilation of Three 
Basement Floors of the Marshall Field Retail Store, Chica- 
go, Jan. 23, 1909. Ventilation of a Newspaper Photo-En- 
graving Plant, June 26, 1909. Ventilation of the First 
Church of Christ, Scientist, Boston, Sept. 19, 1908. The Ven- 
tilation of a Weave Shed, Aug. 8, 1908. Ventilation of the Bat- 
tery Tunnels of the New York Subway Extension to Brook- 
Ivn, Oct. 5, 1907. Railway Tunnel Ventilation, Feb. 20, 1904. 
Raihcay Age Gazette. Detroit Return Trap System, July 23, 
1909, p. 175. Washington Union Station Ventilation, June 

12, 1908, p. 84. Heating and Ventilating the Storage Battery 
Stations on the New York Central & Hudson River. April 

13, 1908, p. 489. Ventilation and Heating of Engine Round- 
houses as Adopted by the New York Central Lines, June 18, 
1909, p. 1335. The Metal Worker. A Remarkable Theatre Ven- 
tilation Plant, Jan. 15, 1910, p. 63. An Interesting Factory 
Ventilation Plant, Jan. 15, 1910, p. 90. Ventilation of Factories, 
Auditoriums, Stores and Schools in Chicago, May 7. 1910, p. 
634. Ventilation in Relation to Health, Wm. G. Snow, June 
25, 1910, p. 866; July 30, 1910, p. 142. Heating and Ventilat- 
ing Plant Complying with Factory Law, July 10. 1909. p. 
41. Heating from a Physician's Standpoint, May 14, 1910, 
p. 658. Ventilating a Restaurant, Sept. 25, 1909, p. 39. 
Cassier's Magazine. The Purification of Air, Oct. 1910. 



CHAPTER III. 



HEAT L.OSSES FROM BUILDINGS. 



21. L1O8S of Heat by Conduction and Radiation: — In 

planning- the heating- system for any building, the first and 
probably the most important part of the work is to esti- 
mate the total heat loss per hour from the building. Un- 
fortunately this is the part which is the least open to 
satisfactory calculations and we find little valuable theo- 
retical data upon the subect. 

Heat is lost from a building in two ways, by radiation 
and by convection, i. e., that transferred through walls, win- 
dows and other exposed surfaces by conduction and lost 
by radiation; -and that carried off by the movement of the 
air as it passes out through the openings in the building 
to the outside air. The radiation loss is' usually of greater 
importance, but the convection loss is of much more im- 
portance than is generally considered. In the average 
building bo^th of these values are difl^cult to determine. 

Radiation losses are considered under various heads, 
such as glass, wall, floor, ceiling and door losses. Concern- 
ing the conduction of heat through these various materials, 
the available data have been obtained by experimentation 
and do not agree very closely. Peclet in France, and Gras- 
hof, Rietschel, Klinger and Rechnagel in Germany, each 
carried on experimental research to determine the heat 
transmission through various materials and structures. 
These published data form the basis for a large part of the 
heat loss calculations of the present time. Much valuable 
material can be found in the more recent writings of 
Hood, Wolff, Box, Carpenter, Kinealy, Allen, Hogan, Hub- 
bard and others, but many of the values quoted are only 
rough approximations at best. The reason for so much 
uncertainty' in this part of the work is found in the fact 
that there are such great differences in methods of build- 
ing^ construction. Conductivity tests for the various ma- 
terials have been satisfactorily made, but when these same 
materials have been put into a building wall the quality 
of the workmanship often permits more heat loss by con- 



46 HEATING AND VENTILATION 

vection than would be transmitted through the materials 
themselves. The values quoted for brick walls and glass 
agree fairly well. The greatest difRculty is found in the 
balloon-framed building with its studded walls, where the 
dead air space in a well constructed wall may be a good 
non-foonductor, or where, on the other hand, the same space 
in a poorly constructed wall may become a circulating air 
space to cool the walls by the movement of the air. 

Table IV has been compiled from a number of the 
best references as stated above, and represents a fair aver- 
age of all of them. The value K (rate of transmission), in 
some of the references, varied for the same material, being 
somewhat greater for small temperature differences than 
where the temperatures differed widely. In general, the 
transfer o-f heat -through any substance is about propor- 
tional to the difference of the temperature between the two 
sides of the substance. This was noticeably true for most 
of the quotations. 

TABLE IV. 

Conductivities of Building Materials. 
£* =: B. t. u. transmitted per sq. ft. per hour per degree dif. 

(Materials. K. 

Brick wall, 8" 4 

Brick wall, 12'' 31 

Brick wall, 16" 26 

Brick wall, 20'' 23 

Brick wall, 24" 21 

Brick wall, 28" 19 

Brick wall, 32" 17 

Brick wall, furred, use .7 times non-furred in each case. 
Stone wall, use 1.5 times brick wall in each case. 

Windows, single glass 1.0 

Windows, double glass 6 

Skylight, single glass 1.1 

Skylight, double glass 7 

Wooden door, 1" 4 

Wooden door 2" 36 

Solid plaster partition, 2" 6 

Solid plaster partition, 3" 5 

Ordinary stud partition, lath and plaster on one side 6 



HEAT LOSSES FROM BUILDINGS 41 

Ordinary stud partition, lath and plaster on two sides.. .34 

Concrete floor on brick arch 2 

Fireproof construction as flooring 1 

Fireproof construction as ceiling" . ; 14 

Single wood floor on brick arch 15 

Double wood floor, plaster beneath 10 

Wooden beams planked over, as flooring 17 

Wooden beams planked over, as ceiling 35 

Walls of the average wooden dwelling 25 to .30 

Lath and plaster ceiling, no floor above 62 

Lath and plaster ceiling, floor above 25 

Steel ceiling, with floor above 35 

Single %" floor, no plaster beneath 45 

Single %" floor, plaster beneath 26 

Occasionally it is convenient to reduce all radiating 
surfaces to equivalent wall surface and take account of the 
heat losses as a part of the wall. 

The following equivalents for doors, floors and ceilings 
have been found to give good results: 

Doors not protected by storm doors or vestibule = 200% of 
equal wall area. 

Floor over unheated space. Air circulation = same as wall. 
Floor over unheated space. Still air = 40% of equal wall area. 
Ceiling below unheated space. Air circulation = 125% of 
equal wall area. 

Ceiling below unheated space. Still air = 50% of equal wall 
area. 

In all references from French and German authorities, 
one is impressed by the extreme care and exactness with 
which every detail is worked out, even to those minor parts 
usually considered in this country of no special moment. 

Table IV has been reduced to chart form, Fig. 12, where 
the table values agree with — 10° outside temperature and 
wind velocity. The application of this chart is as follows: 
Assume the outside temperature — 10°, still air, inside tem- 
perature 70°, south exposure. What is the heat loss from 
a square foot of 12 inch brick wall, also from a square foot 
of single glass window? Beginning at the right of the 
chart at — 10° outside temperature trace to the left to the 
wind velocity, then up the ordinate to the 12 inch wall 



42 



HEATING AND VENTILATION 



(interpolate between 8 and 16), then to the left to the line 
indicating 70*' Inside temperature, then down to the south 
exposure, then to the left showing 25 B. t. u. transmitted 




Fig. 12. 



per hour. For the glass, trace from — 10° to the wind 
velocity, then up to the single window, then to the left to 
the inside temperature, 70**, then down to south exposure. 



ESTIMATION OF HEAT LOSS 43 

then to the left showing" 80 B. t. u. per square foot per hour. 
Checking- this with the table for a 12 inch brick wall we 
have .31 X 80 r= 24.8 B. t. u. For glass 1 X 80 = 80. The 
values given in the table must be increased for west, north 
and east exposures. The effect of the wind velocity upon 
the heat loss is very marked. Locations subjected to high 
winds should have extra allowance made. For example, 
take the 12 inch brick wall just mentioned. Assume the 
wind to be 30 miles an hour. By the same process as before 
we find for a south exposure, 36 B. t. u. loss as compared to 
25 with wind velocity. 

22. Loss of Heat by Air Leakage : — The exact amount 
of air leaving a building by leakage is impossible to de- 
termine. Many experiments have been carried on in the 
last few years to determine the amount of leakage around 
windows and doors. These in the specific cases have been 
successful, but no actual values can be quoted for general 
use. Again, a considerable amount of air passes through 
the walls, thus rendering the case more complicated. In all 
the experiments, however, it has been found that these 
losses have been much greater than was supposed. In rooms 
not heavily exposed, or in touch with heavy winds, two 
chang-es per hour may be safely allowed for all leakage 
losses. 

23. Exposure Losses and Other Losses: — Radiation 
losses are much greater on the exposed or windward side of 
the building. Moving air passing over the surface of any 
radiating material will wipe the heat off faster than would 
be true of still air. The north, north-west and the north- 
east in most sections of the country get the highest winds 
and have the least benefit of the sun and are therefore 
counted the cold portions of the building. In figuring a 
building it is customary to figure each room as though it 
were a south room, which is assumed to need no additions 
for exposure, and then add a certain percentage of this 
loss for exposure to fit the location of the room. The exact 
amount to add in each case is largely a matter of the judg- 
ment of the designer, who, of course, is supposed to know 
the direction of the Jieavy winds and the protection that 
is afforded by surrounding- buildings. A wide variety of 
values covering the American practice might be quoted for 
this, but the following will give satisfactory results: 



44 HEATING AND VENTILATION 

TABLE V. 

North, north-east and north-west rooms heavily exposed, 

10-20 per cent. 

East or west rooms moderately exposed .... 5-10 per cent. 

Rooms heated only periodically 20-40 per cent. 

The German practice is somewhat more extreme than 

ours in this part of the work: 

North, north-east and north-west rooms heavily exposed 

15-25 per cent. 

East and west rooms 10-15 per cent. 

Surfaces exposed to heavy winds 10-20 per cent. 

Heat interrupted daily but rooms kept closed 10 per cent. 

Heat interrupted daily but rooms kept open 30 per cent. 

Heat off for long" periods 50 per cent. 

Rooms 12 to 14^/^ feet from floor to ceiling .. 3 per cent. 

Rooms 14:V2 to 18 feet from floor to ceiling ... 6 per cent. 

Rooms 18 feet and above from floor to ceiling" 10 per cent. 



24. Loss of Heat by Ventilation: — A certain amount of 
fresh air leaks into every building and displaces an equal 
amount of warm air, but this amount of fresh leakage air 
is not considered sufficient for good ventilation. When 
warm air is displaced either by leakage or by ventilation, 
it is exhausted to the outside air and as it leaves the room 
carries a certain amount of heat with it. This is a direct 
loss and should be taken into account. 

Since the loss by leakag-e is practically the same for 
all systems of heating, it is accounted for in the ordinary 
heat loss formula, but losses by ventilating systems must 
be considered in excess of this amount. Let Q' = cubic feet 
of fresh air supplied per hour, f — to =^ drop in temperature 
from the inside to the outside air; then the heat lost by ex- 
hausting the air. Art. 27, is 

Q' (f — to) 
Hv = (9) 

55 

25. Two General Methods of Estimating the Heat Loss H 
from a Building arc in Common Use: — First, estimate all 
radiation losses and add to their sum a certain per cent. 



ESTIMATION OF HEAT LOSS 45 

of itself to allow for leakage by convection; second, esti- 
mate all radiation losses and add to their sum a certain 
amount which depends upon the volume of the room. The 
first is by Equivalent Radiating Surfaces only and the second is 
by Equivalent Radiating Surfaces and Yolume comMned. 

26. Method No. 1: — Figuring by Equivalent Radiating 
Surface. — Let H -~ B. t. u. heat loss from room per hour; 
G — exposed glass in square feet; W = exposed wall minus 
glass, plus exposed doors reduced to equivalent wall surface 
in square feet; F = floor or ceiling separating warm room 
from unheated space; tat = difference between room temper- 
ature and outside temperature; ty = difference between 
room temperature and temperature of the unheated space; 
K, K' and K'' = coefficients of heat transmission; a =z per- 
centage allowed for exposure and 6 = percentage allowed 
for loss by leakage, varying in per cent, of other losses 
from 10 in the average house to 30 in the house of poor 
construction. 

From the above, we have 

H = (KOtx + K'Wtx + K^'Fty) (1 + a + 6) (10) 

(Application. — ^Assume the sitting room. Fig. 15, to have 
a total exposed wall surface, W, exclusive of glass, 242 
square feet; total exposed glass, O, 38 square feet; and 
floor, F, 195 square feet. Assume that all the rooms are 
heated to 70 degrees with an outside temperature of zero 
degrees and that all workmanship is fair. Assume also the 
floor to be of the ordinary thickness and not ceiled below, with 
a temperature below the floor of this room of 32 degrees; 
and that two people are using the room. Under such con- 
ditions what is the heat loss from the room? Since this 
is a south room there is no exposure loss and a = 0. Then 
assuming & =: .20 we have 

£r = (1 X 38 X 70 H- .3 X 242 X 70 + .45 X 195X 38) (1 + .20) 
= 13270 .B. t. u. 

Good judgment will be necessary in selecting the proper 
outside temperature for the calculation. The value of this 
outside temperature varies among men in the same locality 
as miuch as 20 degrees. In the above application if to = — 
20° and the temperature of the unheated space below the 
floor remains at 32 degrees, formula (10) becomes H = 15946 
B. t. u. See discussion of this point under Art. 60. 



46 HEATING AND VENTILATION 

27. Method Xo. 2: — Figuring- by Equivalent Radiating 
Surface and Volume. — The general formula for this is 

H = (KGtx + K'Wtx + K^'Fty + oc nCtx) (1 + o) (11) 

where H, K, Q, tx, ty, W, F and a are as given above; C = cubic 
volume of the room; 7i = number of times the air is sup- 
posed to change in the room by leakage and convection per 

hour, recommended, 1 to 2; oc = -— and is usually taken .02 

55 
for convenience of calculation. This constant refers to the 

heat carried av^'ay by the air. The specific heat of the air 

at 32 degrees is .238; then the number of pounds of air 

heated from 32 to 33 de-rees by 1 B. t. u. is 1 -^ .238 = 4.2. 

Now if the weight of a cubic foot of air at 32 degrees is .0807 

pounds, we would have 4.2 -h .0807 = 52 cubic feet of air 

heated from 32 to 33 degrees by 1 B. t. u. However, most 

of the heating is not done at from 32 to 33 degrees but 

from 32 to 70 degrees, in which case, the volume of air 

heated from 69 to 70 degrees by 1 B. t. u. is 52 X 530 -r- 

492 r= 56 cubic feet. See absolute temperature, Art. 4. It 

is evident that some approximation must here be made. No 

exact value can be taken because of the great range of 

temperature change of the air, but 55 is commonly used 

as the best average. The difficulty of handling formula 

with the constant — — ^^^ led to the simple form .02. (See 

55 
last column Table 12, .Appendix.) 

Application. — With the same room as used in Application 
1, we have, it a = 0, 

-ff =: (1 X 38 X 70 + .3 X 242 X 70 + .45 X 195 X 38 + 
.02 X 1 X 1950 X 70) (1 + O) = 13806 B. t. u. 

28. Method No. 3: — Professor Carpenter reviews the 
work of the various authors and quotes the following 
formula, which is the same as that given in Method No. 2 
in a more simplified form, with the terms the same as 
before; 

H = (Q ^ .25 TF + .02 nC) tx (12) 

In his opinion .the very elaborate methods sometimes used 
are unnecessary. K may be assumed .25 for any ordinary 
wall surface, brick or frame, and the ceilings adjoining an 
attic or the floors above a cellar of the average house need 
not be considered. Floors above an unexcavated space 
where no heat is obtained from the furnace and where there 



ESTIMATION OF HEAT LOSS 47 

is more or less circulation of air should no doubt have 
some allowance. This would probably be the same as given 
in Art. 21. The values of n are quoted by the same author- 
ity as follows: 

Values of n. 



Residence heating-, halls, 3; sitting- room and rooms on the 
first floor, 2; sleeping rooms and rooms on second floor, 1. 
Stores, first floor, 2 to 3; second floor, l^/^ to 2. 
Offices, first floor, 2 to 2i^; second floor, 1% to 2. 
Churches and public assembly rooms, % to 2. 
Larg-e rooms with small exposure, i/^ to 1. 



Application. — Assuming the same room as before, 
H = [38 + .25 (242 + .4 X 195) + .02 X 2 X 1950] 70 = 13720. 

29. Combined Heat Loss E' — {H -\- Hv) : — In buildings 
where ventilation is provided, the total heat loss is that lost 
by radiation, fl", + that lost by ventilation, Ev, Csee also Art. 
36). Letting Qv = cubic feet of air needed per hour for 

ventilation, we have 

Qv tx 

E' — E -\ (13) 

55 

Rule. — -To -find the total heat loss from any huilding, add to 
the heat loss calculated by formula, the amount found hy multiply- 
ing the number of cubic feet of ventilating air exhausted from the 
building per hour by one- fifty -fifth of the difference between the in- 
side and outside temperatures. 

30. Temperatures to be Considered: — The temperature 
maintained in heated rooms in this country is 70 degrees. 
Outside temperatures used in figuring heat losses are gen- 
erally taken, southern part, + 10 degrees; northern part — 
20 degrees; ordinary value, degrees. (See Art. 60.) 

The German Government requires estimates on the fol- 
lowing temperatures, as quoted in "Formulas and Tables 
for Heating," by Prof. J. H. Kinealy. 



48 HEATING AND VENTILATION 

TABLE VI.— Values of t\ 



The temtperatures of heated rooms are generally as- 
sumed by the German Engineers to be as follows: 

Rooms In which the occupants are for the most part at rest: 
Living" rooms, business rooms, court houses, offices, 

schools 6S 

Lecture halls and auditoriums .61 to 64 

Rooms used only as sleeping rooms 54 to 59 

Bath rooms in dwellings 68 to 72 

Sick rooms 72 

Rooms in which the occupants are undergoing bodily ex- 
ertion: 

Workshops, gymnasiums, fencing halls, etc.. in which 

the exertion is vigorous 50 to 59 

Workshops in which the exertion is not so vig- 
orous 61 to 64 

Rooms used as passage rooms or occupied by people in 
street dress: 

Entrance halls, passages, corridors, vestibules 54 to 59 

Churches 50 to .=^4 

Miscellaneous: 

Prisons for the confmement or prisoners during 

the day 64 

Prisons for the confinement of prisoners during 

the night 50 

Hot houses 77 

Cooling houses 59 

Bath houses: 

Swimming halls 68 

Treatment rooms, massage rooms 77 

'Steam bath 113 

f 
Warm air bath 122 

Hot air bath 140 



ESTIMATION OF HEAT LOSS 49 

TABLE VII. 
Values of to When Applied to a Room. 

The temperatures of rooms not heated are quoted a3 
follows, with the outside air at 4 degrees below zero: 

'Cellars and rooms kept closed 32 

Rooms often in communication with the outside air, 
such as passag-es, entrance halls, vestibules, etc. 23 
Attic rooms immediately beneath metal or slate 

roof ]^4 

Attic rooms immediately beneath tile, cement, or 
tar and gravel roof 23 



31. Heat given off from Lights and from Persons 
Within the Room: — As a credit to the heating system, some 
heating- engineers take account of the heat radiated from 

the lights and the persons within the room. The following 
table by Rubner is quoted by Prof. Kinealy: 



TABLE VIII. 



Gas, ordinary split burner, B. t.'u. per candle power hr. 300 
Gas, Argand 
Gas, Auer 
Petroleum 



Electric, incandescent 
Electric, arc 



200 

31 

160 

14 

4.3 

According to Pettenkofer, the mean amount of heat 
given off per person per hour is 400 heat units for adults 
and 200 for children. 



50 HEATING AND VENTILATION 



REFERENCES. 

References on Heat Losses and Radiation. 

Technical Books. 
Snow, Principles of Heat, p. 54. Carpenter, Heating and 
Ventilating Bldgs., p. 64. Hubbard, Power, Heat, and Tent., p. 417. 
Allen, :t^otes on Heat, and Vent., p. 13. 

Technical Periodicals. 
Engineering Review. Air Leakage Around Windows; Its 
Prevention and Effects on Radiation, Harold McGeorge, Feb. 
1910, p. 64. The Heating and Ventilating Magazine. Austrian Co- 
efficients for the Transmission of Heat through Building Ma- 
terials, W. W. Macon, Feb. 1908, p. 36. Air Leakage through 
Windows and its Effect Upon the Amount of Radiation, B. 
S. Harrison, Nov. 1907, p. 18. Air Leakage Around Windows 
and its Prevention, H. W. Whitten, Dec. 1907, p. 20. Deriva- 
tion of Constants for Building Losses, R. C Carpenter, 
March 1907, p. 34. Methods of Estimating Heat Losses from 
Buildings, C. L. Hubbard, Sept. 1907, p. 1. Trans. A. S. H. & 
V. E. Heat Losses and Heat Transmission, Walter Jones, 
Vol. XII, p. 233. Loss of Heat through Walls of Buildings, 
R. C. Carpenter, Vol. VIII, p. 96. Engineering Record . An In- 
vestigation of the Heat Losses in an Electric Power Station, 
Jan. 16, 1909, p. 77. Derivations of Constants for Bldg. 
Losses, R. C. Carpenter, Feb. 23. 1907, p. 214. The Metal Worker. 
Humidity of Air and Its Determination, with Chart, Aug. 21, 
1909, p. 56. Heating Water by Steam, Sept. 18, 1909, p. 53. 
Coal Consumption in Two English Hot Water Heating 
Plants, Sept. 19, 1908, p. 47. School House Warming and 
Ventilation, Serial, Jan. 6, 1906, p. 58. Poicer. Heat Trans- 
mission through Corrugated Iron, A. H. Blackburn. Oct. 29, 
1912. Coal Required to Heat Modern City Building, E. F. 
Tweedy, Jan. 16, 1912. 



CHAPTER IV. 



FURNACE HEATING AND VENTILATING. 



PRINCIPLES OF DESIGN. 

32. Furnace Systems Compared with Other Systems; — 

The plan of heating- residences and other small buildings 
by furnace heat, in which the air serves as a heat carrier, is 
a very common one in this country. Some of the points in 
favor of the furnace system are: low cost of installation, 
heating" combined with ventilation, and the rapidity with 
which the system responds to light service or to sudden 
changes of outdoor temperatures. Compared with that of 
other heating systems, the furnace system can be installed 
for one-third to one-half the cost. In addition to this, the 
fact that ventilation is so easily obtained, and the fact that 
a small fire on a mild day may be sufficient to remove the 
chill from all the rooms, give this method of heating many 
advocates. The objections to the system are: cost of operation 
when outside air is circulated, difficulty of heating the 
windward side of the house, and the contamination of the 
air supply by the fuel gases leaking through the joints in 
the furnace. In a good system w^ell installed, the only 
objection to be seriously considered is the difficulty of heat- 
ing that part of the house subjected to the pressure of the 
heavy wind. The natural draft from a warm air furnace 
is not very strong at best and any differential pressure 
in the various rooms will tend to force the air toward the 
direction of least resistance. The cost of operating can be 
controlled to the satisfaction of the owner, consistent to his 
ideas of the quality of the ventilation needed. Arrange- 
ments may be made to carry the warm air from the room 
back again to the furnace to be reheated, in which case, 
if the fresh air be cut off entirely, the cost of heating is 
about the same as that of any system of direct radiation 
having no provision for ventilation. Any amount of fresh 
air, however, may 1 ^ taken from the outside for the pur- 
pose of ventilation, thus requiring the same amount of air 



52 



HEATING AND VENTILATION 



to be exhausted at the room .temperature and causing an 
increased cost of operation, as discussed in Art. 36. 

33. Essentials of the Furnace System: — Fundamentally, 
this installation must contain: first, a furnace upon proper 
settings; second, a carefully designed and constructed sys- 
tem of fresh air supply and return ducts; and third, the 
warm air distributing leaders, stacks and registers. Fig. 
13 shows, in elevation, a common arrangement of these 
essentials, and gives, also, the air circulation by arrovv 




DAMPER 



Fig. 13. 



directions. The installation shown is rendered flexible In 
operation by the basement dampers, proper adjustment of 
which will allow fresh air to be taken from either side 



FURNACE HEATING 53 

of the house or furnished to the pit under the furnace by the 
duct from the first floor rooms. This return register is 
usually placed in the hall, under the stairway, or in some 
room which is generally in open connection with the other 
rooms on the first floor, as a large living room. 

34. Points to be Calculated in a Furnace Design: — Be- 
sides the calculated heat loss, H, which of course would 
probably be the same for all methods of heating, other 
points in furnace design would be taken up in the follow- 
ing order: first, find the cubic feet of air needed as a 
heat carrier and determine if this amount of air is sufficient 
for ventilation; then calculate the areas of the following: 
net heat register, gross heat register, heat stack, net 
vent register, gross vent register, vent stack, leader pipes, 
fresh air duct and total grate area. From the total grate 
area the furnace may be selected. 

35. Air Circulation in Furnace Heating: — The use of air 

in furnace heating may be considered from two standpoints, 
each very distinct in itself. First, air as a heat carrier; 
second, air as a health preserver. The first may or may not 
provide fresh air; it merely provides enough air to carry 
the required amount of heat from the furnace to the rooms, 
i. e., to take the place of the heat lost by radiation plus 
the small amount that is carried away by the natural in- 
terchange of air from within to without the building, as 
would be true in any residence that is not especially planned 
to provide ventilation. With certain allowable temperatures 
at the various parts of the system, this volume of air may 
be easily calculated. One point here should be remembered: 
when the cubic feet of air per hour as a heat carrier is 
found at the register, this volume remains the same, no 
matter if it enters the furnace through a duct from within 
or without the building. So this plan may be both a heat 
carrier and a ventilator if desired, subject only to the 
amount of air required. The seco- plan requires that 
enough air be sent to the rooms to provide ventilation. If 
this amount is less than that needed as a heat carrier, all 
well and good, the first amount will be used; but if it 
should be greater, then the first amount will need to be 
increased arbitrarily to agree. This increased volume will 
then be used instead of that calculated as a heat carrier 



54 HEATING AND VENTILATION 

only. As previously stated, the cubic feet of air per hour 

as a ventilator may be taken as 1800 N, where N is the 
number of persons to be provided for. See Art. 9. 

36, Air Required per Hour as a Heat Carrier:— A safe 
temperature t, of the circulating air as it leaves the heat 
register, is 130 degrees. This may at times reach 140 de- 
grees but it is not well to use the higher value in the 
calculations. If, as is nearly always the case, the room 
air temperature, t\ is 70 degrees, the incoming air will 
drop in temperature through 60 degrees and, since one cubic 
foot of air can be heated through 55 degrees by one B. t. u. 
(see Art. 27.), it will give ofe 60 -^ 55 = 1.09 (say 1.1) B. t. u. 

Let Q ~ cubic feet of air per hour as a heat carrier; H 
=: total heat loss in B. t. u. per hour by formula; t = tem- 
perature of the air at the register; and f — temperature of 
the room air; then 

g = ^i^ (14) 

t — r 

Rule. — To find the cubic feet of air necessary to carry the heat 
to the rooms, multiply the heat loss calculated by formula by fifty- 
five and divide by the difference between the register and the room 
temperatures. 

For ordinary furnace work this becomes 

H 



Q 



1.1 
Now if this air is not allowed to escape from the building, 
Fig. 13, but is taken back to the furnace and recirculated, 
the only loss of heat will be H, that calculated by the 
formula; but as a matter of fact, air thus used would soon 
become contaminated and wholly unfit for the occupants to 
breathe, hence, it is customary to exhaust through ventil- 
ating flues, either a part or all of the air sent from the 
furnace. This makes an additional loss of heat from 
the building corresponding to the drop in degrees from 70 
to that of the outside air. Let the temperature of the out- 
side air, to, be degrees, then the resulting heat loss would 
be (see also Art. 110 on blower work.) H' = H plus (f — to) 
divided by 55 and multiplied by the amount of air intro- 
duced for ventilation. Stated as a formula for the special 
conditions, this becomes 

H' = H -\- 1.27 Qv (15) 



FURNACE HEATING 55 

Take for illustration the Sitting Room, Pig. 15, and 
consider it under three conditions on a zero day: first, when 
all the air is recirculated; second, when only enough air is 
exhausted to give good fresh air for ventilation; third, 
when all the air is exhausted. Under the first case the loss 
H, by formula is, say, 14000 B. t. u. per hour and no other 
loss is experienced. In the second case, let three people oc- 
cupy the room and allow 1800 cubic feet of fresh air per hour 
for each person, or a total of 5400 cubic feet per hour, then 
the total heat loss from the room will be, Formula 13, 
14000 + 5400 X 70 -> 55 = 20873, say 21000 B. t. u. The 
third case, where all the air is exhausted, gives 14000 -f- 1.1 
= 12727 cubic feet of fresh air exhausted at 70 degrees, 
which requires the same amount of fresh air being raised 
from zero to 70 degrees to replace it. This necessitates the 
application of 12727 X 70 -t- 55 == 16198 B. t. u. additional, 
or a total heat loss of 30198, say 30000 B. t. u. per hour. 

The second condition is that which would be found most 
satisfactory. It is evident from inspection that the cubic 
feet of air necessary as a heat carrier will supply excessive 
air for ventilation in the average residence, and the de- 
signer need not necessarily consider the amount of air for 
ventilation except as he wishes to investigate the size of 
the furnace, the amount of coal burned or the cost of 
heating; the latter being in direct proportion to the respect- 
ive total heat losses. (See also Art. 60.) 

Applicatiox. — Referring to Table IX, page 63, the calcu- 
lated amount of air per hour for the various rooms and for 
the entire building may be found. 

37. Is this Amount of Air Sufficient for Ventilation if 
Taken from the Outside? — Take the 13 X 15 X 10 foot sitting 
room, Fig. 15. Let the estimated heat loss be 14000 B. t. u. 
per hour, then Q — 12727 cubic feet. With a room volume 
of 1950 cubic feet, the air will change 6.5 times per hour, 
and, allowing 1800 cubic feet of air per person, will supply 
seven people with good ventilation if fresh air be used. 
Stated as a formula, this would be 

H H 

N = = approx. (16) 

1.1 X 1800 2000 

As a matter of fact, ventilation for half this number would 
be ample in an ordinary residence room excepting on extraor- 



56 HEATING AND VENTILATION 

dinary occasions. So it would seem that the subject of 
ventilating air will be more than taken care of if the ducts 
and registers are planned to carry air for heating purposes 
only. 

38. Given the Heat Loss H and the Volume of Air Q' for 
any Room, to find t, the Temperature of the Air Entering at 
the Register: — If for any reason Q is not sufficient for ven- 
tilation, then more air must be sent to the room and the 
temperature dropped correspondingly to avoid overheating 
the room. Let Q' — total volume of air per hour, including 
extra air for ventilation, measured at the register, then 

55 n 

f =r 70 + (17) 

Q' 

Rule. — When it is necessary for ventilation purposes to circu- 
late more air than that calculated from the heat loss formula, then 
the temperature at the register will 'be found hy adding to seventy 
degrees the amount found by multiplying the heat loss by fifty -five 
and dividing by the cubic feet of ventilating air. 

Application. — Suppose it were necessary to send 18000 
cubic feet of fresh air to this sitting room per hour to ac- 
commodate ten people, the temiperature of the air at the 
register should be 

55 X 14000 

« = 70 H = 113°. 

18000 

39. Net Heat Registers: — The velocity of the air r, 

as it leaves the heat regisiter, varies from 3 to 4 feet per 

second according to different designers. The first figure 

is objected to by some because it gives too large register 

areas; while the latter value is claimed to be great enough 

that the occupants of the room will notice the movement 

of the air. Practice no doubt tends to the higher velocity. 

Most heat ' registers in residences are placed at the floor 

line. If, however, they be placed above the heads of the 

occupants of the room (see Art. 102), higher velocities than 

the ones named can be used. The general formula for net 

registers is 

H X 55 X 144 

y. H. R. = (18) 

(t — V) X r X 3600 

Rule. — To find the square inches of net heat register, multiply 
the heat loss calculated by formula by tioo and tivo-tenths and di- 
vide by the product of the velocity in feet per second times the 
difference in temperature between the register and the room air. 



FURNACE HEATING 57 

Assuming a mean velocity of 3.5 feet per second, and 
60 degrees drop in temperature from the register to the 
room, then the square inches of net register for any room 
are found by the formula: 

fl"X 55 X 144 

N. H. R. = = .01 H (19) 

60X3.5X3600 

40. Net Vent Registers: — Vent registers should be put 
in with any furnace plant, although this is not always done. 
In order that any room may be heated properly, it is abso- 
lutely necessary that the cold air in the room be allowed 
to escape to give room for the heated air to come in. This 
in some cases is done by venting through doors, windows 
or transoms. A tightly closed room cannot be properly 
heated by a furnace. 

If all the air were to pass out the vent register at the 
same velocity as it entered through the heat register, the 
area of the vent register would be to the area of the heat 
register as the ratio of the absolute temperatures of the 
leaving and entering air; that is, the area of the vent 
register =i .9 of the area of the heat register. As a matter 
of fact, since some of the air leaves* the room through other 
openings, the vent register need not be so large. Practice 
has decided this area to be about 

N. y. R. — .008 H = .S N. H, R. (20) 

41. Gross Register Area: — The nominal size, or catalog 
size, of the register is usually stated as the two dimensions 
of the rectangular opening into which it fits, and varies 
from 1.5 to 2 times the net area. The larger value is prob- 
ably the safer to .follow unless the exact value be known 
for any special make of register. Floor registers have 
heavier bars and consequently for the same net area have 
somewhat larger gross area. 

G. R. = (1.5 to 2) times the net register (21) 

Round registers may be had if desired. Register sizes may 
be found in Tables 17 and 19, Appendix. 

42. Heat Stacks: — To get the proper sizes of the stacks 
In any heating system is a very important part of the de- 
sign of that system. By some designers the cross sectional 
area is taken roughly as a certain ratio to that of the net 



58 HEATING AND VENTILATION 

register. This has been quoted anywhere from 50 to 90 
per cent. Such wide variations between extremes of air 
velocity should certainly require careful application. Prof. 
Carpenter in H. and V. B. Arts. 54 and 141, suggests 4, 5 
and 6 feet per second respectively, as the air velocities for 
the first, second and third floors. Mr. J. P. Bird, in the 
"Metal Worker" of Dec. 16, 1905, uses 280, 400 and 500 feet 
per minute, which is approximately 4.5, 6.5 and 8 feet per 
second under like conditions. The formula for cross sec- 
tional area of the heat stack, from formula 19, then becomes, 
if the velocities are 4, 5.5 and 7 feet per second. 



H X 55 X 144 r. 0091 Hist floor! 

n. S. = =< . 0066 H 2nd floor ^ (22) 

60 X (4, 5.5 or 7) X 3600 L. 0052 J? 3rd floorj 

Rule. — See rule under net heat registers loith changed value 
for velocity. 

The air velocity in the stack is based upon the formula 

t? = V2gh, where h = (effective height of stack) X (* — f) -r 
(460 + f); V is in feet per second; t is the temperature of 
the stack air and f is the temperature of the room air. 
The calculated results from this formula are much higher 
than those obtained in practice because of the shape of 
cross sections of the stack, the friction of its sides and the 
abrupt turns in it. 

From the basis of the net register (figured at 3.5 feet 
per second) the two quotations by Carpenter a.-d Bird give 
heat stack areas as follows: first floor, 80 to 88 per 
cent.; second floor, 55 to 70 per cent.; and third floor, 44 to 
60 per cent. Good sized stacks are always advisable (see 
Art. 55), but because of the limited space between the stud- 
ding it becomes necessary at times to put in a stack that 
is too small or to increase the thickness of the wall, a thing 
which the architect is occasionally unwilling to do. From 
the above figures, checked by existing plants that are 
working satisfactorily, the following approximate figures, 
reduced to the basis of the net heat register area, will no 
doubt give good results. 

r.8 times the net heat register. 1st floor -\ 
H. 8, =i .66 times the net heat register. 2nd floor y (23) 
L.5 times the net heat register. 3rd floorj 

43. Vent Stacks:— Y. S. = .S E. S. (24) 



44. Leader Pipes: — Since all the air that passes through 
the stacks must pass through the leader pipes, it seems 



FURNACE HEATING 59 

reasonable to assume that the areas of the two would be 
equal. It must be remembered, however, that the stacks, 
because of their vertical position, offer less resistance in 
friction, while on the other hand the leader pipes, being 
nearly horizontal and having more crooks and turns in 
them, will have considerable friction and will consequently 
retard the air to a greater degree. There will also be some 
loss of temperature in the air as it passes through the 
leader pipes, consequently the volume of air entering the 
leader from the furnace will be greater than that going 
up the stack. 

It would be well, from the above reasons, to make the 
area of the leader pipes 

L. P. = (1.1 to 1.2) times the stack area, (25) 

the exact figures to depend upon the length and inclination 
of the leader sCnd the selection of the diameter of the pipe. 

45. Fresh Air Ducts — The area of the fresh air duct is 
• determined largely by experience as in the case of the vent 

register. It is generally taken 

F. A. D. = .8 times the total area of the leaders. (26) 

Assume the average velocity of the air in the leaders to be 
6 feet per second and the area of the fresh air duct to be 
as shown above, then, if the air in each were of the same 
temperature, the velocity in the fresh air duct would be 
6 -^ .8 =: 7.5 feet per second; but since the temperatures 
are different the velocities will be in proportion to the ab- 
solute temperatures. Hence it is, at degrees, .78 X 7.5 — 
5.8; at 25 degrees, .82 X 7.5 = 6.2; and at 50 degrees, .88 
X 7.5 = 6.6 feet per second. It is seen by this, that al- 
though the area of the fresh air duct is contracted to 80 
per cent, of that of the leaders, the velocity is in all 
cases below that of the leaders. It is always well to have 
a fresh air duct that is large in cross sectional area and 
free from obstructions and sharp turns. 

46. Grate Area: — The grate area of a furnace is esti- 
mated from the total heat lost from the building, figured 
on a basis of a certain degree of ventilation. In obtaining 
the grate area it is necessary to assume the quality of the 
coal, the efficiency of the furnace and the pounds of coal 
burned per hour per square foot of grate. The quality of 



60 HEATING AND VENTILATION 

coal selected would be between 12000 and 14000 B. t. u. per 
pound as shown in Table 14, Appendix. The efficiency of 
the average furnace is about 60 per cent., and the coal 
burned per square foot of grate per hour ranges from 3 to 
7 pounds. Concerning the last point there may be a wide 
difference of opinion. Higher temperatures in the combus- 
tion chamber are conducive to economy, because of the 
radiant heat of the fire; hence, to reduce the size 
of the fire pot, and fire small amounts of coal with 
greater frequency Would seem to be the ideal way. On 
the other hand, with high temperatures in the combustion 
chamber, the loss up the chimney is increased. Probably 
the one factor which is most effective in settling this point 
is the inconvenience of frequent firing. Furnaces are 
charged from two to four times each twenty-four hours. 
This requires a good sized fire pot and a possibility of 
banking the fires. To allow 5 pounds per hour is probably 
as good an average as can be made for most coals in fur- 
nace work. 

Let E' = total heat loss from the building including 
ventilation loss; E = efficiency of the furnace; f = value of 
coal in B. t. u. per pound; and p =^ pounds of coal burned 
per square foot of grate per hour; then the formula for the 
square inches of grate area is 

H' X 144 

O. A. = (27) 

E X f X p 

Rule. — To find the square inches of grate area for any furnace, 
multiply the total heat loss from the building per hour hy one 
hundred and forty-four and divide l>y the quantity found hy multi- 
plying the total pounds of coal burned per hour hy the heat value of 
the coal and the efficiency of the furnace. 

Application. — In the typical illustration, the total heat loss 
on a zero day by formula is, say, 100000 B. t. u. per hour. 
This will require 90909 cubic feet of air as a heat carrier. 
Assuming as a maximum that 10 people will be in the 
house and that they will need 18000 cubic feet of fresh air 
per hour for ventilation, this air will carry away approx- 
imately 22900 B. t. u. per hour, making a total heat loss 
from the building of 122900 B. t. u. per hour. Now, if the 
furnace is 60 per cent, efficient and burns 5 pounds of 
14000 B. t. u. coal per hour per square foot of grate, we 
will have 

122900 X 144 

0, A. =: = 421 square inches = 23.2 inches 

.60 X 14000 X 5 



FURNACE HEATING 61 

diameter. With coal at 13000 B. t. u. per pound, the grate 
would be 454 square inches or 24 inches diameter. In either 
case a 24 inch grate would be selected. With the assump- 
tions as made above, the formula becomes G. A, = .0035 H' 
for the better grade of coal, and O. A. = .0037 E^ for the 
poorer grade, from which the following approximate form- 
ula may be taken: 

G, A. square inches = .0036 H' (28) 

47. Healing Surface: — The amount of heating surface 
to be required in any furnace is rather an indefinite quantity. 
Manufacturers differ upon this point. Some standard may 
soon be looked for but at present only rough approximations 
can be stated. One of the chief difficulties is in determin- 
ing what is, or what is not, heating surface. Some quota- 
tions no doubt include some surface in the furnace that is 
very inefficient. In estimating, only prime heating surface 
should be considered, i. e., such plates or materials having 
direct contact with the heated flue gases on one side and 
the warm air current on the other. If these plates trans- 
mit K, B. t. u. per square foot per degree difference of tem- 
perature, tg, per hour; if, also, one square foot of grate 
gives to the building E X f X p ^. t. u. per hour, there will 
be the following ratio between the heating surface and 
grate surface: 

H. 8. E f p 

= (29) 

G. 8. Etz 

Application. — Let the value K tz be 2500, as suggested by 
W. G. Snow, Trans. A. S. H. & V. E., 1906, page 133, and 
with the same notations as in Art. 46 obtain 

H. 8. .6 X 14000 X 5 
= = 17 



G. 8. 2500 

In practice this ratio varies anywhere between 12 and 30. 

In the investigations being made by the Federal Fur- 
nace League their furnaces show an average of 1^ square 
feet of direct heating surface and 1 square foot of indirect 
heating surface per pound of coal burned in the furnaces 
per hour, making a total of 2^ square feet of heating sur- 
face per pound of coal burned per hour. The average size 
of the furnaces submitted for tests, and probably the aver- 
age size of furnaces used in actual practice, have a top fire- 



62 HEATING AND VENTILATION 

pot diameter of 24 inches and a bottom fire-pot diameter of 
21 inches, making an average fire-pot diameter of 22% inches 
and an average cross-sectional area of 2.83 square feet. 
The average depth of pot in this size of furnace is about 
131/^ inches, and for the purpose of rating under the Fed- 
eral System would burn 7.2 pounds of coal per hour per 
square foot of average fire-pot cross-section, making the 
ratio per square foot of grate surface about 8^/4 pounds of 
coal per hour. This gives a ratio of heating surface to 
grate surface of approximately 20 to 1. 

48. Application of the Above Formulas to a Ten Room 
Residence: — In every design the calculations should be made 
very complete ani the results tabulated for easy reference 
and as a means of comparison. Such a tabulation is shown 
in Table IX, giving all the calculated quantities necessary in 
the installation of the furnace system illustrated in Figs. 
14, 15 and 16. The value of so condensing the work will be 
readily apparent. The tabulation of the values used 
for the various terms of the formula facilitates checking 
and the detection of errors. Plans should be carefully 
drawn to scale sLnd accompanied by a sectional elevation. 
The scale should be as large as can conveniently be made. 
The location of the building with reference to the points 
of the compass should always be given, as well as the 
heights of ceilings and the principal dimensions of each 
room. There will be a wide variety of practica in making 
allowance for exposure, floors, ceilings, closets and small 
rooms not considered of sufficient importance to have inde- 
pendent heat. The personal element enters into this part of 
the work very largely. Such points as these are left to 
the discretion oif the designer who, after having had con- 
siderable experience is able to judge each case very closely. 



FURNACE HEATING 



63 



TABLE IX. 

Formula. H = {Q + .25 TF + .02 wC) 70 





•i-i 

m 


IS 

•iH 

ft 




CI 

3 





-a 

o 


o 


1 




u 








G 


38 

85 

78 

2 

14000 

12727 

140 

14x16 


28 

28 

84 

2 

10800 

9818 

108 

12x14 


42 

52 

78 

2 

13250 

12045 

132 

14x16 


28 

65 

55 

2 

11900 

10818 

119 

12x14 


29 
73 

104 
3 
14000 
12727 

140 
14x16 


42 

45 

35 

1 

9400 

8544 

94 

12x12 

61 

67 

75 

10x12 

45 


38 

60 

36 

1 

9850 

8954 

98 

12x12 

64 

70 

78 

10x12 

48 


28 

26 

31 

1 

6600 

6000 

66 
9x12 

43 

47 

53 
8x10 

32 


28 

30 

22 

1 

5600 

5091 

56 
8x10 

36 

40 

45 
8x10 

27 


14 

17 

26 

2 

4400 

4000 

44 

8x10 

28 

31 

35 

8x8 

22 


315 
481 


.25 TT" 


.02 ?i C _ 




n 




H 


99800 


G 


Area of Net Heat Register 

Heat Reg ster Size 

Area of Heat Stack____ 




Area of Leader 

Area of Net Vent Register 

Vent Register Size 

A rea of Vent Stacl( 


100 

112 

12x14 

67 


77 

86 

10x12 

52 


94 

106 

12x14 

64 


85 

95 

12x12 

60 


100 

112 

12x14 

67 


711 


Remarks 


u 

§ 
8 

< 


1 

o 
u 


u 

ft 

o 

i-l 

a; 

a 

o 
o 

< 


u 

ri 

ft 

l| 

I— 1 "^ 

< 


i! 

< 


9 

m 
O 
ft 
X 
O 

+^ 

o 

u 

<D 
ft 

o 

1— 1 

o 


+3 
© 

w. 
O 

O 

g 

;-( 




5 


+3 

a; 

M 
U 

rt CD 

a> 

1-' 


a 

8 
2 

1 


< 


+3 





i? 

^'^ 

^ 

5 





Diameter of grate allowing- ventilation for ten people = 
24 inches. Cold air duct = 569 square inches = 18 X 32 inches. 

In selecting the various stacks and leaders it would be 
well to standardize as much as possible and avoid the extra 
expense of installing so many sizes. This can be done if 
the net area is not sacrificed. 



64 



HEATING AND VENTILATION 




FOUNDATION PLAN. 

Ceiling 6'. 

Fig. 14. 



FURNACE HEATING 



t>5 




~ 



_I 






1^ Dl^^mG Roon. f*^ ^tudy. 




VUaSi. 



FIRST FLOOR PLAN. 
Ceiling 10'. 

Fig. 15. 



S6 



HEATING AND VENTILATION 




SECOND FLOOR PLAN. 
Ceiling 9'. 

Fig. 16. 



CHAPTER V. 



FURNACE HEATING AND VENTILATING. 



SUGGESTIONS OX THE SELECTION AND INSTALLATION OF 
EURNACE HEATING PARTS. 

49. Selection of the Furnace: — In selecting- a furnace 
for residence use or other heating service, special attention 
should be paid to the following points: easy movement of 
the air, arrangement and amount of heating surface, shape 
and size of the fire-pot, method of feeding fuel to the fire 
and type and size of the grate. The furnace gases and the 
air to be heated should not be allowed to pass through the 
furnace in too large a unit volume or at too high a velocity. 
The gases should be broken up in relatively small volumes, 
thus giving an opportunity for a large heating surface. 
Concerning the gas passages themselves, it may be said 
that a number of small, thin passages will be found more 
efficient than one large passage of equal total area. This 
is plainly shown in a similar case by comparing the effi- 
ciency of the water-tube or tubular boiler with that of 
the old fashioned flue boiler; i. e., a large heating surface 
is of prime importance. Again, it is desirable that the 
total flue area within the furnace should be great enough 
to allow the passage of large volumes of air at low velocities, 
rather than small volumes at high velocities. This permits 
of less forcing of the fire and consequently lowers the tem- 
perature of the heating surface. The latter point will be 
found valuable when it is remembered that metal at high 
temperatures transmits through its body a greater amount 
of impure gases from the coal than when at low tempera- 
tures. Concerning velocities, it may be said that on account 
of the low rate of transmission of heat to or from the 
gases, long flue passages are necessary, so that gases mov- 
ing at a normal rate will have time to give off or to take 
up a maximum amount of heat before leaving the furnace. 
Air is heated chiefly by actual contact with heated sur- 
faces and not much by radiation. Consequently, the ef- 
ficiency of a furnace is increased when it is designed so 
that the gases and air in their movement impinge perpen- 



68 



HEATING AND VENTILATION 



dicularly upon the heated surfaces at certain places. This 
point should not be so exaggerated that there would be 
serious interference with the draft. The efficiency is also 
increased if the general movement of the two currents be 
in opposite directions. 

Furnaces for residences are usually of the portable type. 
Fig. 17, the same being enclosed in an outer shell composed 
of two metal casings having a dead air space or an asbes- 
tos insulation between them. Some of the larger gized 




Fig. 17. 



plants, however, have the furnace enclosed in a permanent 
casement of brick work, as in Fig. 18. Each of the two 
types of furnaces give good results. The points usually 
governing the selection between portable and permanent 
settings are price and available floor space. 

The cylindrical fire-pot is pro'bab'ly better than a con- 
ical or spherical one, there being less danger of the fire 
clogging and becoming dirty. A lined fire-pot is better 
than an unlined one, because a hotter fire can be maintained 
in it with less detriment to the furnace. There is of course 
a loss of heating surface in the lined pot, and in some forms 



FURNACE HEATING 



69 



of furnaces the fire-pot is unlined to obtain this increased 
heating- surface. It seems reasonable to assume, however, 
that the lined pot is longer lived and contaminates the air 
supply less. 




Fig. 18. 




70 



HEATING AND VENTILATION 



Some form of shaking* or dumping grate should be se- 
lected, as a stationary grate is far from satisfactory. Care 
s-hould be exercised also, in the selection of the movable 
grate, as some forms not only stir up the fire but permit 
much of it to fall through to waste when being operated. 

The fuel is fed to the fire-pot from the door above the 
fire. This is called a top-feed furnace. In some forms, how- 
ever, the fuel is fed up through the grate. This is called 
the under-feed furnace, Fig-, 19, and is rapidly gaining in 
favor. The latter type requires a rotary ring grate with 
the fuel entering up through its center. 

The size of the furnaee may be obtained from the estimated 
heating capacity in cubic feet of room space as g'iven in the 
sample Table 18, Appendix. Another and p-erhaps a bet- 
ter way, and one that serves as a good check on the above, 
is to select a furnace from the calculated grate area. See Art. 
46. Having selected the furnace by the grate area, check 
this with the" table for the estimated heating capacity 
and the heating surface to see if they ag-ree. 

What is known as a combination heater is shown in 
Fig. 20. It is used for heating part of the rooms of a resi- 
dence by warm air, as in 
regular furnace work, and 
the remainder of the rooms 
by hot water. In this 
manner, rooms to be ven- 
tilated as well as heated 
may be connected by the 
proper stacks and leaders 
to the warm air deliveries 
of such a combination 
heater, while rooms requir- 
ing less ventilation or heat 
only may have radiators 
installed and connected to 
the flow and return pipes 
shown in the figure. Also, 
because of the difficulty 
in heating certain exposed 
rooms with warm air, these 
rooms may be supplied by 
^'^^' ^^* the positive heat of the 

more reliable water circulation. 




FURNACE HEATING 71 

50. liOcation of Furnace: — TV^here other thing's do 
not interfere, a furnace should be set as near the center 
of the house plan as possible. Where this is not wise or 
possible, preference should be given to the colder sides, say 
the north or west. In any case, it is advisable to have the 
leader pipes as near the same length as can be made. The 
length of the smoke pipe should be as short as possible, 
but it will be better to have a moderately long smoke pipe 
and obtain a more uniform length of leader pipes than to 
have a short smoke pipe and leaders of widely different 
lengths. 

The furnace should be set low enough to get a good 
upward slope to the leaders from the furnace to their re- 
spective stacks. This should be not less than one inch per foot 
of length and more if possible. These leader pipes should be 
dampered near the furnace. 

The location of the furnace will call forth the best 
judgment of the designer, since the right or wrong decis- 
ion here can make or mar the whole system more com- 
pletely than in any other manner. 

51. Foundation: — All furnaces should have directions 
from the manufacturer to govern the setting. Each type of 
furnace requires a special setting and the maker should 
best be able to supply this desired information concerning 
it. Such information may be safely followed. In any case 
the furnace should be mounted on a level brick or concrete 
foundation specially prepared and well finished with cement 
mortar on the inside, since this interior is in contact with 
the fresh air supply. 

62. Fresh Air Duct: — This is best constructed of hard 
burned brick, vitrified tile or concrete, laid in four inch 
walls with cement mortar and plastered inside with ce- 
ment plaster, all to be air tight. The top should be covered 
with flag stones with tight joints. The riser from this, 
leading to the outside of the building, may be of wood, tile 
or galvanized iron^ and the fresh air entrance should be 
vertically screened. The whole should be with tight joints 
and so constructed as to be free from surface drainage, 
dirt, rats and other vermin. This duct may be made of 
metal or boards as substitutes for the brick, tile or concrete. 
Board construction is not so satisfactory, although it is the 
cheapest, and whenever used should be carefully constructed. 



72 



HEATING AND VENTILATION 



In addition to the opening- for the adniission of the 
fresh air duct, another opening may be made under the 
furnace for the purpose of admitting the duct which carries 
the recirculated air from the rooms to the furnace. Both 
of these ducts should have dampers that may be opened or 



>i 'I 11 11 



!!°^I'-!l?l! 



liii'??'!'^'' 




E5H AIR RETU 




TURN 



FRONT 



FRONT 



FRONT 

Fig. 21. 

closed. See Figs. 13 and 21. Both ducts should also be provid- 
ed with doors that can be opened temporarily to the cellar 
air. Sometimes it is desirable to have two or more fresh 
air ducts leading- from the different sides of the house to the 

furnace so as to get the benefit of 
any change in air pressure on the 
outside of the building-. 

Proper arrangements may be 
made for pans of clear water in the 
air duct near the furnace to give 
moisture to the air current, although 
only a small amount of moisture 
will be taken up at this point. In 
most cases where moistening pans 
are used, they are installed in con- 
nection with the furnace itself. A 
J^^mm ] I ^^P good way to moisten the air is to 
wZi^^^Z^ k k wZ^ have moistening pans built in just 

behind the register face, Fig". 22. 
These pans are shallow and should 
not be permitted to seriously inter- 
fere with the amount of air enter- 
ing- through the register. 
53. Recirculating Duct: — A duct should be provided 
from some point within the building-^ through the cellar 
and entering into the bottom of the furnace. This is to car- 




FURNACE HEATING 



73 



ry the warm air from the room back to the furnace to be 
reheated for use again wnithin the building-. In many cases 
tin or galvanized iron is used for the material for the 
recirculating pipe. Where this enters the furnace it 
sihould be planned with sufficient turn so that the 
air would be projected thro'Ugh the furnace, ^t-hus 
placing a hindrance to the fresh cold air from following 
back through this pipe to the rooms. The exact location 
of the same will depend, of course, on the location of the 
register installed for this purpose. The construction of the 
duct may agree with the similar construction of the fresh 
air duct. 

54. Leader Pipes: — All leader pipes should be round 
and free from unnecessary turns. They should be made 




Fig. 23. 



HEATING AND VENTILATION 



from heavy galvanized iron or tin and should be laid to an 
upward pitch of not less than one inch per foot of length, 
and more if it can possibly be given. The connections with 
the furnace should be straight, but if a turn is necessary, 
provide long radius elbows. All connections to risers or 
stacks should be made through long radius elbows. Rect- 
angular shaped hoots having attached collars are sometimes 
used, but these are not so satisfactory because of the im- 
pingement of the air against the flat side of the stack; also 
because of the danger of the leader entering too far into 
the stack and thus shutting off the draft. Leaders should 
connect to the first floor registers by long radius el- 
bows. Leader pipes should have as few joints as possible 
and these should be made firm and air tight. Fig. 23 shows 
different methods of connecting between leaders and stacks, 
also between leaders and registers. 

The outside of all leader pipes should be covered to 
avoid heat loss and to provide additional safety to the plant. 
The covering is usually one or more thicknesses of asbes- 
tos paper or mineral wool. 

55. Stackjs or Risers: — The vertical air pipes leading to 
the registers are called stacks or risers. They are rect- 
angular or oblong in section and are usu- 
ally fitted within the wall. See Fig. 24. 
The size of the studding and the distances 
they are set, center to center, limit the 
effective area of the stack. All stacks 
should be insulated to protect the wood- 
work. This is done by making the stack 
small enough to clear the woodwork by 
at least one-quarter inch and then wrap- 
ping it with some non-conducting material 
such as asbestos paper held in place by 
wire. 

Another way, and one which is prob- 
ably more satisfactory, is to have pat- 
ented double walled stacks having an air 
space between the walls all around. The 
outside wall is usually provided with vent 
holes whicji allow the circulation of air 
between the walls, thus protecting any 
one part from becoming overheated. All 
Fig. 24. stacks should be made with tight joints 




FURNACE HEATING 75 

and should have ears or flaps for fastening" to the studding". 
Patented sacks are made in standard sizes and of various 
leng*ths. The sizes ordinarily found in practice arQ about 
as given in Table 19, Appendix. 

A stack is sometimes run up in a corner or in some 
recess in the wall of a room where its appearance, after 
being" finished in color to compare with that of the room, 
would not be unsightly. This is necessary in any case 
where the stack is installed after the building is finished. 
This method is desired by some because of its additional 
safety and because more stack area may be obtained than 
is possible when placed within a thin wall. 

All stacks should be located in partition walls looking 
toward the outside or cold side of the room. This protects 
the air current from excessive loss of heat, as would be the 
case in the outside walls. It also provides a more uniform 
distribution of air. 

The area of the stack best adapted to any given room 
is another point in furnace work which brings out a wide 
diversity of practice. Results from different installations 
show variations as great as 50 per cent. This is not so 
noticeable in the first floor rooms as it is in those of the 
second floor. In a great many cases the architect specifies 
light partition walls between large upper rooms, say, four 
inch studding set sixteen inch centers, between twelve foot 
by fifteen foot rooms, heavily exposed. From theoretical 
calculation of heat losses, these rooms require larger stacks 
than can be placed between studding as stated; however, it 
is very common to find such rooms provided for in this way. 
One possible excuse for it may be the fact that the room is 
designed for a chamber and not for a living room. Any 
sacrifice in heating capacity in any room, even though it be 
used as a sleeping room only, should be done at the sug- 
gestion of the purchaser and not at the suggestion of the 
architect or engineer. Every room should be provided with 
facilities for heat as though it were to be used as a living 
room in the coldest weather, then there would be fewer 
complaints of defective heating plants and less migrating 
from one side of the house to the other on cold days. 

This lack of heating capacity for any room is some- 
times overcome by providing two stacks and registers in- 



76 



HEATING AND VENTILATION 



stead of one. This plan is very satisfactory because one 
of the registers may be shut off in moderate weather; how- 
ever, it requires an additional expense which is scarcely 
justified. A possible improvement would be for the archi- 
tect to anticipate such conditions and provide suitable 
partition walls so that ample stack area could be put in. 
The ideal conditions will be reached when the architect act- 
ually provides air shafts of sufficient size to accommodate 
either a round or a nearly square stack. When this time 
comes a great many of the furnace heating" difficulties wilJ 
have been solved. 

A double stack supplying air to two rooms is some- 
times used, having a partition separating the air currents 
near the upper end. This practice is questionable because 
of the liability of the pressure of air in the room On the 
cold side of the house forcing the heated air to the other 
room. A better method is to have a stack for each room 
to be heated. 

56. Vent Stacks: — Vent stacks should be placed on the 
inner or partition walls and should lead to the attic. They 
may there be gathered together in one duct leading to a 
vent through the roof if desired. 

57. Air Circulation Witliin tlie Room: — The location of 
the heat register, relative to the vent register, will deter- 




Fig. 25. 



FURNACE HEATINC 77 

mine to a large degree the circulation of the air within the 
room. Fig". 25, a, b, c and d, shows clearly the effect of the 
different locations. The best plan, from the standpoint of 
heating, is to enter the air at a point above the heads of the 
occupants and Ts^ithdraw it from the floor line, at or near the 
same side from which the air enters. This gives a more uni- 
form distribution as shown by the last figure. It is doubtful, 
however, if this method will give the best ventilation in 
crowded rooms where the foul air naturally collects at the 
top of the room. Furnace heating is not so well cared for 
in this regard as are the other forms of indirect heating, the 
air being admitted at the floor line and required to flnd its 
own way out. 

58. Fan-Furnace Heating System: — In large furnace 
installations where the air is carried in long ducts that are 
nearly, if not quite, horizontal, and where a continuous sup- 
ply of air is a necessity in all parts of the building, a com- 
bination fan and furnace system may be installed. These 
are frequently found in hospitals, schools and churches. Such 
a system- may be properly designated a mechanical warm 
air system. In comparison with other mechanical systems, 
however, it is simpler and cheaper. The arrangement may 
be illustrated by Fig. 96 with the tempering coils omitted 
and the furnace substituted for the heating coils. The fan 
should always be between the air inlet and the furnace so as 
to keep a slight pressure above atmosphere on the air side 
and thus reduce the leakage of the fuel gas through the 
joints of the furnace. By this arrangement there is less 
volume of air to be handled by the fan and a smaller sized 
fan may be used. 

Fan-furnace systems may be set in multiple if desired, 1. 
e., one fan operating in connection with two or more fur- 
naces. 

Fig. 26 represents a two-furnace plant showing the 
fan and the two furnaces. The air is drawn into the fresh 
air room through a grate in the outside wall and is forced 
through the fan to the furnaces where it divides and passes 
up through each furnace to the warm air ducts. Part of 
the fresh air from the fan is by-passed over the top of the 
furnaces and is admitted to the warm air ducts through 
mdxing dampers. These dampers control the amount of 
hot and cold air for any desired temperature of the mix- 



78 



HEATING AND VENTILATION 




^\\\\\XS^\\ \^A^v^^\\\\\\^V\\\\\\^^ 



Fi! 



•^^5. 



ture. Temperature control may be applied, also air washing 
and humidifying- apparatus can be installed and operated 
with satisfaction. Paddle wheel fans are preferred, al- 
thoug-h the disk wheel may be used where the pipes are 
large and where the air must be carried but short distances. 
For fan types see Chapter X. 

59. Suggestions for Operating Furnaces! — Furnaces are 
desig-nated hard coal and soft coal, depending upon the type and 
the construction of the grate, hence the grade of coal best 
adapted to the furnace should be used. The size of the open- 
ings in the grate should determine the size of the coal used. 

Keep the fire-pot well filled with coal and have it evenly 
distributed over the grate. 



FURNACE HEATING 79 

Keep the fire clean. Clinkers should be removed from 
the fire once or twice daily. It is not necessary to stir the 
fire so completely as to waste the coal through the grate. 

When replenishing" a poor fire do not shake the fire, but 
put some coal on and open the drafts. After the coal is well 
ignited clean the fire. 

The ash pit should be frequently cleaned, because an 
accumulation of ashes below the grate soon warps the grate 
and burns it out. 

Keep all the dampers set and properly working. 

Have a damper in the smoke pipe and keep it open only 
so far as is necessary to create a draft. 

Keep the water pans full of water. 

'Clean the furnace and smoke pipe thoroughly in all parts 
at least once each year. 

Keep the fresh air duct free from rubbish and impurities. 

Allow plenty of pure fresh air to enter the furnace. In 
cold weather part of this supply may be cut off. 

Have the basement well ventilated by means of outside 
wall ventilators, or by special ducts leading to the attic. 
Never permit the basement air to be circulated to the living 
rooms. 

To bank the fires for the night, clean the fire, push the 
coals near the rear of the grate, cover with fresh fuel to 
the necessary depth (this will be found by experience), set the 
drafts so they are nearly closed and open the fire doors 
slightly. 

60. Determination of the Best Outside Temperature to 
Use in Design and the Costs Involved in Heating by Fur- 
naces: — As a basis for the work of the heating and venti- 
lating engineer it is necessary that he be well acquainted 
with the temperature conditions in the locality where his 
services are employed. He should compile a chart showing 
extreme and average temperatures covering a period of 
j'ears and with this chart a fairly safe estimate may be 
made upon the costs involved in operating any heating 
and ventilating system during any part of the average 
season or throughout the entire heating season. Any costs 
of operation arrived at are only illustrative of method and 
probability, however. All one can say is that if the tem- 
perature in any one season averages what is shown by the 
average curve for the period of years investigated, then 
the cost in operating the system may be easily shown by 



80 HEATING AND VENTILATION 

calculation. Costs in heating are relative figures only and 
cannot be predetermined exactly except under test condi- 
tions. The heating engineer should also know the mini- 
mum outside temperatures covering a period of years in 
that locality so as to determine upon an outside tempera- 
ture for his design vt^ork. Any design is somewhat of a 
compromise between average conditions and the minimum 
or extreme conditions, approaching the extreme rather than 
the average. Patrons are willing that the heating systems 
be designed so as to give normal temperatures in the rooms 
on all but a few of the coldest days. These minimum con- 
ditions usually have a duration of from two to three days 
and it would not be considered good engineering from an 
economic standpoint to design the system large enough to 
heat to normal inside temperature on the coldest day ex- 
perienced in a period of years. The plant would be too 
large and would require too much financial in-put. As an 
illustration of the method of obtaining the outside tem- 
perature to be used in design, also methods of determining 
approximate costs for heating, see Fig. 27. This has been 
worked up as an average for the temperatures of each of 
the days respectively between September fifteenth and May 
fifteenth, covering a period of thirty years, at Lincoln, 
Nebraska. The minimum temperature curve includes the 
outside temperatures for December 1911, and January 1912, 
which may be regarded as a period of unusual severity. 
Referring to the chart it will be seen that a cold period of 
one month was experienced from December nineteenth to 
January twenty-first, reaching its minimum temperature of 
. — 26° on January twelfth. If this curve were assumed to 
be the most' severe weather that would be found in this 
locality, then by a study of conditions one may easily de- 
termine a good value for outside temperature in design. 
There were twenty days when the temperature was below 
zero, twelve days below — 5°, six days below — 10°, four 
days below — 15°, two days below — 20°, and a part of one 
day below — 25°. Each of the extreme and sudden drops 
were such as to last from two to three days and were only 
experienced in two or three instances. It is very evident 
that a system designed for 0° outside would fall far short 
of the requirement even when put under heavy stress. On 
the other hand one de&igned for — 25° outside would actu- 
ally come up to its capacity for only a part of one day out 



FURNACE HEATING 



81 



of the 240 heating" days. One designed for — 10° would 
fulfill conditions Avithout forcing excepting at two or three 
periods of very short duration, at which times the system 
could be forced sufficiently without detriment. The per- 



TEMPCRATURE IN OLGREES ANO HEAT LOSS IN THOUSAND 6TU 



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sonal equation enters into the calculation of the heat loss 
somewhat and there will be some difference of opinion con- 
cerning which to use, — 10° or — 15°. Probably the latter 
would be a safer value. All that is necessary is to plan 



82 



HEATING AND VENTILATION 



for ample service at all but one or two of the cold periods 
of short duration and the system w-ill be considered very 
satisfactory from the standpoint of size and capacity. Any 
additional amount put in would be an investment of money, 
which is scarcely justified for the small percentage of time 
that this additional capacity would be called for. 

After the minimum outside temperature has been de- 
cided and the plant is designed, one would like to know 
the probable expense in handling such a plant throughout 
the heating season. Assume an inside temperature through' 
out the building of 70°. Combine the two half months, Sep- 
tember and May, into one month, and take the average of 
these average temperatures for the days of each month, 
thus giving the drop in temperature between the inside 
and the outside of the building. The heat loss from the 
building is then proportional to these drops in tempera- 
ture. In this case the differences are as follows: 

iSeptember + May 7° below 70° 

October 17° 

November 32.3° 

December 44° 

January 4S.7° 

February 45° 

March 34° 

April 19.5° 

Taking the sum of all these differences as the total, 
100%, and dividing each individual difference by the total, 
we have the percentages of loss for the various months 
as follows: 



September + May 2.84% of total yearly loss 

October 6.9 % " 

Novem»ber 13.1 % " 

December 17.8 % " 

January 19.7 % " 

February 18.2%" 

March 13.7 % " 

April 7.9 % " 

These percentages of loss indicate what may be ex- 
pected in the expense for coal at various times of the heat- 
ing year, based upon the average temperatures existing in 
the past thirty years. From this the heat loss has been 



FURNACE HEATING- 83 

calculated for the sample design stated under Furnace 
Heating". The results are shown upon the chart in tons 
of coal per year, assuming that the entire house is heated 
to 70° upon the inside for each hour between September 
fifteenth and May fifteenth. The lowest curve is that for 
direct radiation only. The next superimposed curve as- 
sumes fresh air for ten people. The third curve assumes 
one-half of the required air to be recirculated and the upper 
curve assumes all the air to be fresh air. 



Si HEATING AND VENTILATION 

REFERENCES. 
References on Furnace Heating. 

Technical Books. 

Snow, Prin. of Heat, p. 27. Snow, Furnace Heat, p. 7. I. C. S. 
Prin. of Heat d Tent., p. 1237. Carpenter, Heat & Vent. Bldgs., p. 

310. Hubbard, Power, Heat & Yent., p. 423. 

Technical Periodicals. 

Engineering Review. Warm Air Furnace Heating, C. L. Hub- 
bard, Nov. 1909, p. 42; Dec. 1909, p. 45; Jan. 1910, p. 66; Feb. 
1910, p. 48; March 1910, p. 51; May 1910, p. 48; Aug-. 1910, p. 
29. Warm Air System of Heating- and Ventilating, R. H. 
Bradley, May 1910, p. 32. Mechanical Furnace. Heating and 
Ventilating, June 1910, p. 49. Heating and Vent. System 
Installed in Public School, Fairview, N. J-, July .1910, p. 47. 
Combined System of Warm Air and Hot Water Heat, for a 
Residence, Jan. 1909, p. 26. Warm Air Heating Installation 
in a Brooklyn Residence, March 1909, p. 38. The Heating and 
Ventilating Magazine. Advanced Methods of Warm Air Heat- 
ing, A. O. Jones, Aug. 1904, p. 88. Air Pipes, Sizes Required 
for Low Velocities, Oct. 1905, p. 7. Report of Committee 
(A. S. H. V. E.) to Collect Data on Furnace Heating, Jan, 
1906, p. 35. An Improved Application of Hot Air Heating, 
A. O. Jones, July 1906, p. 31. The Official Federal Fur- 
nace League Method of Testing Furnaces, W. F. Col- 
bert, July 1910. Domestic Engineering. Sanitation in Hot 
Air Heating, James C. Bayles, Vol. 25, No. 6, Sept. 
25, 1903, p. 2 61. Trans. A. S. H. & "f E. Test of Hot Air Grav- 
ity System. R. C. Carpenter, Vol. IX, p. 111. Heat Radiators 
Using Air Instead of Water and Steam, Geo. Aylsworth, Vol. 
IX, p. 259. Velocities in Pipes and Registers in a Warm Air 
System, Vol. XII, p. 352. Relative Size Hot Air Pipes, Vol. 
XIII, p. 270. Velocity of Air in Ducts, Vol. VII, p. 162. The 
Metal Worker. Battery of Furnaces with Vent Ducts, Jan. 15, 
1910, p. 85. Air Blast System, Jan. 15, 1910, p. 93. Origin 
and Comparative Cost of Trunk Main Furnace System, 
Aug. 6, 1910, p. 171. Example of Trunk Line Furnace Piping, 
April 2, 1910, p. 463. Furnace System with Piping 50 ft. Long, 
July 3, 1909, p. 45. Heat Unit in Furnace Heating, Aug. 8, 

1908, p. 43. Data on a Notable School Heating Plant, Nov. 6, 

1909, p. 37. Fan-Furnace Residence System, Oct. 3, 1908, 
p.. 43. Theoretical Construction in Designing Furnace Heat- 
ing, Dec. 26, 1908, p. 33. School Fan Furnace Heating 
Plant, Oct. 8, 1910. Combination Heating in Cold Terri- 
tory, Sept. 29, 1911. Underwriters' Tests of W^all Stacks, 
July 1, 1911. Design of Fan Blast Heating, H. C. Russell, 
Jan. 21, 191,1; Feb. 25. 1911. 



CHAPTER VI. 



HOT WATER AXD STEA3I HEATING. 



DESCEIPTIOX A^'D CIASSIFICATIOX OF THE SYSTEMS. 

61. Hot Water and Steam Systems Compared to Fur- 
nace Systems: — As compared to the warm air or furnace 
plant, the hot water and the steam installations are more 
complicated in the number of parts; they use a more cum- 
bersome heat carrying" medium, for which a return path to 
the boiler must be provided; and have parts, in the form 
of radiators, which occupy valuable room space. But the 
steam and hot water plants have the advantage in that 
their circulations, and hence their transference of heat, 
are quite positive, and not affected by wind pressures. A 
hot water or a steam system will carry heat just as readily 
to the windward side of a house as it will to the leeward 
side, a point which, with a furnace installation, is known 
to be quite impossible. Furnace heating, on the other hand, 
has the advantage of inherent ventilation, while the hot 
water and steam systems, as usually installed, provide no 
ventilation except that due to air leakage. 

62. The Parts of Hot Water and Steam Systems: — ^A hot 

water or a steam system may be said to consist of three 
principal parts: first, the boiler or heat generator; second, 
the radiators or heat distributors; and third, the connecting 
pipe-lines, which provide the circuit paths for the hot water 
or the steam. In the hot water system it is essential that 
the heat generator be loco.ted at the lowest point in the 
circuit, for, as was explained in Art. 5, the only motive 
force is that due to the convection of the water. In the 
steam system this is not essential, as the pressure of the 
steam forces it outward to the farthest points of the system. 
The water of condensation may or may not be returned by 
gravity to the boiler. Hence, with a steam system a radiator 
may be placed below the boiler, if its condensation be trapped 
or otherwise taken care of. 



86 



HEATING AND VENTILATION 



63. Definitions: — In speaking of the piping of heating 
Installations, several terms, commonly used by heating en- 
gineers, should be thoroughly understood. The large pipes 
in the basement connected directly to the source of heat, 
and serving as feeders or distributors of the heating me- 
dium to the pipes running vertically in the building, are 
known as mains. The flow mains are those carrying steam 





Fig. 28. 



P ig. 29. 



or hot water from the source of heat towards the radiators, 
and the return mains are those carrying water or 
condensation from the radiators to the source of 
heat. Those vertical pipes in a building to which 
the radiators are directly connected are called risers, 
while the short horizontal pipes from risers to radi- 
ators are usually termed riser arms. As there are flow 
mains and return mains, so also, there are flow risers and 
return risers. A radiator should have at least two tappings, 
one below for the entry of the heating medium, and one 
on the end section opposite, near the top for air discharge 
as shown by the connected steam radiator of Pig. 2S. It 
may have three, a flow tapping and a return tapping at the 
bottom of the two end sections, and the third or air tapping 
near the top of the end section at the return end as shown 
by the connected hot water radiator of Fig. 29. A return 



HOT WATER AND STEAM HEATING 



87 



main traversing" the basement above the water line of the 
boiler is designated as a dry return and carries both steam 
and water of condensation; one in such position below the 
water line as to be filled with water is designated a wet 
return, and the returns of all two-pipe radiators connecting 
with w^et returns are said to be sealed. 

64. Classification: — One classification of hot water and 
steam systems is based upon the position and manner in 
which the radiators are used. The system which is, per- 
haps, most familiar is the one wherein radiators are placed 
directly within the space to be heated. This heating is ac- 





Fig. 30. 



Fig. 31. 



complished by direct radiation and by air convection cur- 
rents through the radiators, no provision being- made for a 
change of air in the room. This is known as the direct 
system, and, while it causes movements of the air in the 
Toom» it produces no real ventilation. See Fig. 30. 

1.^ the direct -indirect system, the radiator is also 
placed within the space or room to be heated, but its lower 
half is so encased and connected to the outside of the build- 



88 



HEATING AND VENTILATION 



ing that fresh air is continually drawn up through the 
radiator, is heated, and thrown out into the room as shown 
by Fig. 31. Thus is es<tablished a ventilating system more 
or less effective. 

In the purely inclirect system, Fig. 32, the radiating sur- 
face is erected somewhere remote from the rooms to be 
heated, and ducts carry the heated air from the radiator 
to the rooms either by natural convection, as in some in- 
stallations, or by fan or blower pressure, as in others. 
^yhen all the radiation for an entire building is installed 




Fig. 32. 

together in one basement room, and each room of the build- 
ing has carried to it, its share of heat by forced air through 
ducts from one large centralized fan or blower, the system 
is called a Plenum System, and is given special consideration 
in Chapters X to XII. 

65. A second classification of steam and hot water sys- 
tems is made according to the method of pipe connection 
between the heat generator and the radiation. That known 
as the one-pipe system, Fig. 33, is the simplest in construc- 
tion and is preferred by many for the steam installations. 
As the name indicates, its distinguishing feature is the 
single pipe leading from the source of heat to the radiator, 
the steam and the returning condensation both using this 
path. In the risers and connections, the steam and ♦^•on- 
densation flow in opposite directions, thus requiring larger 
pipes than where a flow and a return are both provided. 
In this system the condensation usually flows with the 
steam in the main, and not against it, until it reaches such 
a point that it may be dripped to a separate return 
and then led to the boiler. In -the so-called one-pipe 
hot water system, radiators have two tappings and two 



HOT WATEli AND STEAM HEATING 



Sd 




Fig-. 33. 
risers, but the flow riser is tapped out of the top of the 
single basement main, while the return riser is tapped into 
the bottom of that same main by either of the special fit- 
tings shown in section in Fig. 34, The theory is that the 
hot water from the boiler travels 
along the top of the horizontal base- 
ment main, while the cooler water from 
the radiators travels along the bottom 
of this same main. Hence the neces- 
sity for tapping flow risers out of the 
top and return risers into the bottom 
of this main, thus avoiding a mixing 
of the two streams. Where mains are 
short and straight as in the smaller 
Fig. 34. residence installations, this system 




90 



HEATING AND VENTILATION 



seems to give satisfaction; but it is very evident that, where 
basement mains are long" and more complicated, a mixing 
of the two streams is unavoidable, thus rendering the sys- 
tem unreliable. 

The two-pipe system is used on both s-team and hot 
water installations. For steam work it is probably no 
better than the one-pipe system but for hot -water work it 
is much preferred. In this system two separate and dis- 
tinct paths may be traced from any radiator to the source 
of heat. In the basement are two mains, the flow and the 
return, and the risers from these are always run in pairs, 
the flow riser on one side of a tier of radiators, the return 
riser on the other side. A two-pipe steam system must 
have a sealed return. Typical two-pipe main and riser con- 
nections are shown in Pig. 35. 



Q g » 




Fig. 35. 



Fig. 3 6. 



66. A third system, known as the attic main, or Mills 
system, has found much favor with heating engineers in 
the installation of the larger steam plants although it could 
be applied as well to the larger hot water plants. The 
distinguishing feature, when applied to a steam system, 
is the double main and single riser, so arranged that the 
condensation and live steam flow in the same direction. 



HOT WATER AND STEAM HEATING 91 

This is accomplished by taking- the live steam directly to 
the attic by one large main, which there branches, as need 
be, to supply the various risers, only one riser being used 
for each tier of radiators and the direction of flow of both 
steam and condensation in risers being downward. Hence, 
this system avoids the unsightliness of duplicate risers, as 
in the two-pipe system, and avoids the disadvantage of the 
one-pipe basement system, the last named having steam 
and condensation flowing in opposite directions in the same 
pipe. Fig. 36 shows two common methods of connecting 
risers and radiators with this system. 

67. Diagrams for Steam and Hot Water Piping Systems: 

— >Figs. 37 to 43 inclusive show somie of the methods for 
connecting up piping systems between the source of heat 
and the radiators. At the radiators A, B, C and D are shown 
different methods of connecting between the radiators and 
mains. In every case the various forms of branches below 
the floor and behind the radiators are for the purpose of 
taking up the expansion. It will be noticed that the two- 
pipe steam systems have sealed returns where they enter 
the main return above the water line of the boiler. 

In some steam systems where atmospheric pressure is 
maintained, special valves with graduated control admit steam, 
to the upper part of the radiator. The returns enter into a 
receiver near the boiler with a vapor and air relief to the 
atmosphere through some form of condenser, having an out- 
let pipe leading to an air shaft or to a chimney. The pres- 
sure upon this return is maintained in such a case approx- 
imately 14.7 pounds. The water type of radiator is used, 
having the sections connected both top and bottom and with 
this graduated control only that amount of radiation which 
is necessary to heat the room on a given day is employed. 
Such a system is economical, safe and can be operated In 
connection with any kind of radiation. lig. 43 is typical of 
such systems. 



92 



HEATING AND VENTILATION 



ONE PIPE STEAM SYSTEM -BASEMENT MAIN 




Fig. 37, 



TWO PIPE STEAM SYSTEM-BASEMENT MAIN 




Fig. 38. 



HOT WATER AND STEAM .HEATING 



93 



MILLS SYSTEM 



m 



B 





XL OBv RETURN 

1 n — 



T3Z=B 



STEAM- ATTiC MAIN 




D 




WET RETURN 



•^ 



B§ 



DRY RETURN 






a 



i^^--. 



WET RETURN 



Fig-. 3y. 



ONE PIPE ^5Y5TEM-H0T WATER 




Fig-. 40. 



94 



HEATING AND VENTILATION 



TWO PIPL SYSTEM HOT WATER -BASE ME NT MAIN 




Ai^ 



a& 




Ek 



B 




S-K 




D 



Q 







O: 



^ 



CZZ] 

OS 



o 



Fig. 41. 



f=G=^^ 




-TO EXPANSION TANK 



MILLS SYSTEM 



^opfc 



B 






€=tnt 





O » 



HOT WATER -ATTIC MAN 




^ 



m= 



mp 



CI] 

C3-EI1 
Fig". 42, 




HOT WATER AND STEAM HEATING 



95 



VAPOR SYSTEM OF STEAM HEATINO 




Fig-. 43. 



68. Accelerated Hot AVater Heating Systems: — Improve- 
ments have been devised for hot water heating whereby the 
circulation of the water is increased above that obtained by 
^the open tank system. By increasing the velocity of the 
water, pipe sizes may be reduced, resulting in an economy 
in the cost of pipe and fittings. In addition to this, where 
the temperature of the water is carried above that due to 
atmospheric pressure, the radiation may theoretically be 
reduced below that for the open tank system. How far 
these economies may be pursued in designing is a question 
which should be very carefully considered. In many cases 
the amiount of radiation is kept the same and the chief dif- 
ference merely th^at of pipe sizes. This article is descriptive 
of several of the types of accelerated systems in use and is 
not intended as a critical analysis of the merits of any one 
as compared to the others. 

Of all the principles employed for accelerating the cir- 
culating water, four w'ill be mentioned. First, by increas- 
ing the pressure of the open tank system thus raising the 
temperature above 212 degrees. Second, by superheating a 
part or all of the circulating water as it passes through the 
heater and condensing the steam thus formed by mixing it 



96 



HEATING AND VENTILATION 



with a portion of the cold circulating- water of the return. 
Third, by introducing- steam or air into the main riser pipe 
near the top of the system. Fourth, by mechanically oper- 
ated pumps or motors. 

Descriptive of the first principle, Fig. 44 shows a mer- 
cury-seal tube connected between the upper point of the 
^ main riser and the expansion tank. This is 

.< designed to hold a pressure of about 10 pounds 

»- 

gage, the water from the system filling- the 

casement and pressing" down upon the top 
of the mercury in the bowl. Increasing- the 
pressure in the system lowers the level of the 
mercury in the bowl and forces the mercury 
up the central tube A until the differential 
pressure is neutralized by the static head of 
the mercury. If the pressure becomes great 
enough to drop the. level of the mercury to 
the tube entrance, water and steam will force 
through the mercury to chamber D and from 
thence through the expansion tank to the over- 
flow. Any mercury forced out of the tube A 
by the velocity of the water and steam, strikes 
the deflecting plate G and drops back through 
the annular opening B to the mercury bulb 
below. As the pressure is reduced in the 
system the mercury drops in tube A to the 
level of that in the bulb and water from the 
Fig. 44 expansion tank passes down through the 
mercury-seal into the heating- system to replace any that 
has been forced out to the expansion tank. This action is 
autom.atic and is controlled entirely by the pressure within 
the system. The only loss, if any, is 'that amount Which 
goes out the overflow. The above represents essentially 
what is known as the Honeyw^ell System of .acceleration. 
A modification of the above is used in the Cripps System. 
In this the mercury-seal is placed beyond the expansion 
tank and puts the expansion tank under pressure. 

The second principle is illustrated by Figs. 45 and 46. 
Fig. 45, known as the Koerting System, has a series cf 
motor pipes leading from the upper part of the heater to a 
mixer, where the steam is condensed before it reaches the 




HOT WATER AND STEAM HEATING 



97 



expansion tank by the T\-ater entering throug-h the by-pass 
from the return. The velocity of the steam and water 
tliroug-h the motor pipes and the partial vacuum caused by 
the condensation in the mixer produces the acceleration up 
the flow pipe. 



"31 



EXP TANK 
FLOW 




DVERTLO^* 




Fig. 45. 



Fig. 46. 



In the Jorgensen and Bruchner Systems the heater K 
delivers the hot water up the flow pipe to a regulator 7?, 
where a separation takes place between the steam particles 
and the water, .thus causing an acceleration up the motor 
pipe to the expansion tank A. The water in the flow pipe 2 
is probably near to the temperature of that in 1. After 
passing through the radiators the water in 3 is a't a lower 
temperature than that in 2. The steam particles which 
have collected in the expansion tank A above the water line 
are condensed in T. The acceleration in the system is thu^ 
produced by a combination of the upward movement of the 
steam particles in motor pipe 1 "and the induced upward 
current in 3 toward the condenser Y. It will be noticed 
in the figures that the condensation in one system takes 
place before the expansion tank and in the other system after 



98 



HEATING AND VlUNTll^ATlON 



it has passed the expansion tank. Each of the systems illus- 
trated may be carried under pressure by a safety valve as 
at B or by an expansion tank located high enough to give 
sufficient static head. 

The third principle is v/ell shown by what is known as 
the Reck System. Fig. 47 is a diagrammatic view and Fig. 
48 a detail of the accelerating part of the system. The 



rr^l 





^t^ 



Fig. 47. 



DETAIL OF A^B.AND C 
Fig. 48. 



water passes directly from the heater up the main riser 
where it enters the condenser C and thence into the expan- 
sion tank A as a supply to the flow pipes of the system. 
Steam from a separate boiler is admitted to the mixer B 
above the condenser and enters the circulating water just 
below the expansion tank. The velocity of the steam and 
the partial vacuum caused by the condensation induces a 
current up the flow pipe to the expansion tank. W'hen the 
"water level in the expansion tank reaches the top of the 
overflow pipe the water returns to the steam boiler through 
the condenser C where it gives off heat to the upper cur- 
rent of the circulating water. It will be seen that the 



HOT WATER AND STEAM HEATING 



99 



water in the system and the steam from the boiler unite 
from the inlet at the mixer to the expansion tank. On all 
other parts of the sys-tems they are independent. 

Fig-. 49 is a modification of this same principle, wherein 
air is injected in the riser pipe at B and causes the acceler- 
ation by a combination of the par- 
tial vacuum produced by the steam 
condensation as just mentioned and 
the upward current of the air par- 
ticles as in an air lift. Steam enters 
through the pipe J and ejector H to 
the mixer at B where it is con- 
densed. In passing through H air plow 
is drawn from the tank E and en- 
ters the main riser with the steam. 
The upward movement of this air 
through the motor pipe to the tank 
induces an upward flow of the water 
in the main riser. By this combina- 
tion there are formed three com- 
plete circuits, water, steam and air, 
uniting- as one circuit from the mix- 
er B to the expansion tank E. The Fig. 49. 
steam furnished in principle 3 may be supplied by a separate 
steam boiler or by steam coils in the fire box of a hot water 
boiler. 

In the fourth principle the acceleration is produced by 
some piece of mechanism as a pump or motor placed direct- 
ly in the circuit. This principle is discussed under District 
Heating- and will be omitted here. 

69. Vacuum Systems for Steam: — Most com'monly, the 
systems mentioned, when steam, are installed as the so- 
called low pressure systems, which term indicates an abso- 
lute pressure of about 18 pounds per square inch or 3^/^ 
pounds gage pressure. On extensive work, it has been 
found advantageous to install a vacuum system to increase 
economy, also to insure positive steam circulation by prompt 
removal of condensation through vacuum returns. Even 
for comparatively small residence installations vacuum ap- 
plications of various kinds are becoming common. 

Vacuum sj^stems may be divided into two classes, ac- 
cording to the way in which the vacuum is maintained. For 




100 



HEATING AND VENTILATION 




comparatively small plants, not using" exhaust steam, the 
vacuum is maintained by mercury seal connections, and 
these plants are usually referred to as mercury seal vacuum 
systems. These mercury seals may be attached to any 
standard one or two-pipe system by merely replacing- the 
ordinary air valve by a special connection, which in real- 
ity is only a barometer. An iron tube. Fig. 50, dips just 
below the surface of the mercury in the well on the floor 
and extends vertically to the radiator air trap- 
ping to which the tube connects by a fitting 
which will allow air to pass into and through 
the barometer, but will not allow steam to 
pass. When the system is first fired up and 
steam is raised to several pounds gage, the air 
leaves all the radiators by bubbling through 
the mercury seal at the end of the vertical 
iron tube. If the fire is then allowed to go out, 
the steam will condense, and produce an almost 
perfect vacuum in the entire system, provided 
all pipe fitting has been carefully done. This 
system may be operated as a vacuum system 
at 4 or 5 pounds absolute pressure and have 
the water boiling as low as 150 to 160 degrees. 
The flexibility of this system recommends it 
highly. Applied to a residence or store, the 
plant may be operated during the day at sev- 
eral pounds gage pressure, if necessary, but 
when fires are banked for the night, steam re- 
mains in all pipes and radiators as long as the 
temperature of the water does not fall much 
below 150 degrees. This is in sharp contrast 
with the ordinary system, where steam disap- 
pears from all radiators as soon as the water 
temperature drops below 212 degrees. The 
promptness with which heat may be obtained in the morn- 
ing is noteworthy, for, if the vacuum has been maintained, 
steam will begin to circulate as soon as the water has been 
raised to about 150 degrees. According to demands of the 
weather, the radiators may be kept at any temperature 
along the range of 150 to 220 degrees, thus giving great 
flexibility. 



^ 



^ 



J 



Fig. 50. 



HOT WATER AND STEAM HEATING 



101 



Instead of having- a barometric tube at each radiator, 
one mercury seal may be supplied in the basement, and the 
air tappings of all radiators connected to the top of the 
tube by % inch piping". The Trane vacuum system is usually 
so installed, and is an excellent example of this vacuum 
type. 

The second class of vacuum systems includes those 
designed especially for use in office buildings, and where- 
in the vacuum is maintained by an aspirator, exhauster or 
pump of some description. This exhauster may handle only 





^ 



Fig. 51. 



Fig. 52. 



the air of the sj^stem, that is, it may be connected only 
to the air tappings of all radiators, as in the Paul system. 
Fig. 51, or the exhauster may handle both air and con- 
densation and be connected to the return tappings of all 
radiators, as in the Webster system, Fig. 52. The Paul 
system is fundamentally a one-pipe system, using exhaust 
or live steam and maintaining its circulation without back 
pressure, by exhausting each radiator at its air tapping, 
and also exhausting the condensation from the basement 
tank in which it has been collected by gravity. For an 



102 HEATING AND VENTILATION 

aspirator this system uses either air, steam, or hot water, 
as the conditions may determine. The Webster system is 
fundamentally a two-pipe system and exhausts from the 
radiators both the air and water of condensation, all radi- 
ator returns being connected to the (usually) steam driven 
vacuum pump. These systems are designed to use both exhaust 
and live steam, and hence are finding wide application in the 
modern heating of manufacturing plants. See also Chapter 
IX. 



CHAPTER VIL 



HOT WATER AND STEAM HEATIIVG. 



RADIATORS, BOILERS, FITTINGS AND APPLIANCES. 

The various systems just described are merely different 
ways of connecting" the source of heat to the distributors 
of heat, i. e., methods of pipe connections between heater 
and radiators. Many forms of radiators exist, as well as 
many types of heaters and boilers, each adapted to its own 
peculiar condition. It is in this choice of the best adapted 
material that the heating" engineer shows the degree of 
his practical training, and the closeness with which he fol- 
lows the latest inventions, improvements and applications. 

70. Classification as to Material: — Radiators may be 
classified, according to material, as cast iron radiators, 
pressed steel radiators and pipe coil radiators. Cast radi- 
ators have the hollow sections cast as one piece, of iron. 
The wall is usually about 14 inch to % inch thick, and is 
finally tested to a pressure of 100 pounds per square inch. 
Sections are joined by wrought iron or malleable nipples 
which, at the same time, serve to make passageways be- 
tween any one section and its neighbors for the current of 
heating medium, whether of steam or hot water. Cast iron 
radiators have the disadvantage of heavy weight, danger 
of breaking by freezing, occupying much space, and having 
a comparatively large internal volume, averaging a pint and 
a half per square foot of surface. 

Pressed radiators are made of sheet steel of No. 16 
gage, and, after assembly, are galvanized both inside and 
out. Each section is composed of two pressed sheets that 
are joined together by a double seam as shown at a, Fig. 
53, which illustrates a section through a two-column unit. 




Fig. 53. 

The joints between the sections or units are of the same 
kind. It is readily seen that such construction tends to- 
ward a very compact radiating surface. Pressed radia- 



104 HEATING AND VENTILATION 

tors are comparatively new, but, in their development, 
^ promise much in the way of a light, compact radiation. In 
comparison with the cast iron radiators, they are free from 
the sand and dirt on the inside, thus causing less trouble 
with valves and traps. The internal volume will approxi- 
mate one pint per square foot of surface. See Pig. 54. 

Radiators composed of pipes, in various forms, are 
commonly referred to as coil radiators. They are daily 
becoming less common for direct and direct-indirect work, 
because of their extreme unsightliness. Piping is still 
much used as the heat radiator in indirect and plenum 
systems, although both cast and pressed radiators are now 
designed for both of these purposes where low pressure 
st^am is used. In all coil radiator work, no matter for 
what purpose, 1 inch pipe is the standard size. However, 
in some cases pipes are used as large as 2 inches in diam- 
eter. Standard 1 inch pipe is rated at 1 square foot of heat- 
ing surface per 3 lineal feet and has about 1 pint of con- 
taining capacity per square foot of surface. 

71. Classification as to Form: — Radiators may again be 
classified in accordance with form, into the one, two, three, 
and four-column floor types, the wall type, and the flue 
type. See Fig. 54. These terms refer only to cast and 
pressed radiators. By the column of a radiator is meant 
one of the unit fluid-containing elements of which a sec- 
tion is composed. When the section has only one part or 
vertical division, it is called a single-column or one-column 
type; when there are two such divisions, a two-column; 
when three, a three-column; and when four, a four- 
column type. What is known as the wall type radiator is 
a cast section one-column type so designed as to be of 
the least practicable thickness. It presents the appear- 
ance, often, of a heavy grating, and is so made as to 
have from 5 to 9 square feet of surface, according to the 
size of the section. One-column floor radiators made with- 
out feet are often used as wall radiators. A flue radiator 
is a very broad type of the one-column radiator, the parts 
being so designed that the air entering between the sections 
at the base is compelled to travel to the top of the sections 
before leaving the radiator. This type is therefore well 
adapted to direct-indirect work. See Fig. 54. 



HOT WATER AND STEAM HEATING 



105 





*^ M 




Stairway Type Dining: Room Type Flue Type Circular Type 



CAST RADIATORS 







Wall Type 



Two-Column 

Type 



Three-Column 
Type 



Four-Column 
Type 



PRESSED RADIATORS 




Single-Column Two-Column Three-Column Wall Type 

Type Type Type 



Fig. 54. 



106 HEATING AND VENTILATION 

Many special shapes of assembled radiators will be 
met with, but they will always be of some one of the fun- 
damental types mentioned above. For instance, there are 
"stairway radiators," built up of successive heights of 
sections, so as to fit along the triangular shaped wall under 
stairways; there are "pantry" radiators built up of sections 
so as to form a tier of heated shelves; there are "dining 
room" radiators with an oven-like arrangement built into 
their center; and there are "window radiators" built with 
low sections in the middle and higher ones at either end, 
so as to fit neatly around a low window. Fig. 54 shows a 
number of these common forms as used in practice. 

72. Classification as to Heating Medium: — A third class- 
ification of radiators, according to heating medium em- 
ployed, gives rise to the terms steam radiator and hot 
water radiator. Casually, one would notice little difference 
between the two, but in construction there is a vital differ- 
ence. Steam radiation has the sections joined by nipples 
along the bottom only, but hot water radiation has them 
joined along the top as well. This is quite essential to the 
proper circulation of the water. Steam radiation is always 
tapped for pipe connections at the bottom. Hot water rad- 
iation may have the flow connection enter at the top, and 
the return connection leave at the bottom, or may have 
both connections at the bottom. Hot water radiation can 
b heated very successfully with steam, but steam radia- 
tion cannot be used with hot water. 

73. High versus Low Radiators: — In the adoption of a 
radiator height, the governing feature is usually the space 
allowed for the radiator. Thus, if a radiator of 26 inches 
in height requires so many sections as to become too long, 
then a 32 inch or a 38 inch section may be taken. In gen- 
eral, however, low radiators should be used as far as 
possible, for, with a high radiator, the air passing up along 
the sides of the sections becomes heated before reaching the 
top, and therefore receives less heat from the upper half 
of the radiator, since the temperature difference here is 
small. Hence, the statement that low radiators are more 
efficient, that is, will transmit more B. t. u. per square 
foot per hour than will the high radiators. 

The amount of heat that will be transmitted through a 
radiator to a room is controlled also by the width of the 



HOT WATER AND STEAM HEATING 107 

radiator, harrow radiators being- more efficient than wide 
ones. Considering" both height and number of columns the 
rate of transmission, used in formulas 30 and 31 as 1.7, would 
change to: 

1 column radiator, 30'' high 1.8 B. t. u. 
2 and 3 " " 30'' " l.T 

4 ** '* 30" ** 1.6 

For high and low radiators this may be reduced or increased 
ten per cent, respectively for a 48 inch and a 16 inch radiator. 

74. Effect of Condition of Radiator Surface on the 
Transmission of Heat: — The efficiency of a radiator depends 
very largely upon the condition of its outer surface, a 
rough surface giving off very much more heat than a 
smooth surface. Painting, bronzing, ishellacing or cover- 
ing the radiatoT in a,ny manner affects the ability of the 
'radiator to impart heat to the air circulatimg around it. 
Various te.sts bearing upon this question have been con- 
ducted, agreeing fairly well in general results. A series 
of tests conducted by Prof. Allen at the University of 
Michigan, indicated that the ordinary bronzes of copper, 
zinc or aluminum caused a reduction in the efficiency below 
that of the ordinary rough surface of the radiator of 
about 25 per cent., while white zinc paint and white enamel 
gave tlie greatest efficiencj% being slightly above that of 
the originail surface Numerous coats of paint, even as high 
as twelve, seemed to affect the efficiency in no appreciable 
manner, it being the last or outer coat that always de- 
termined at what rate the radiator would transmit its heat. 

75. Amount of Surface Presented by Various Radiators:-^ 

Table X, gives, according to the columns and heights, 
the number of square feet of heating surface per section 
in cast and pressed radiators. This table will be found to 
present, in very compact form, the similar and much more 
extended tables in the various manufacturers' catalogs. 
An approximate rule supplementing this table and giving, 
to a very fair degree of accuracy, the square feet of sur- 
face in any standard radiator section, is as follows: mul- 
tiply the height of the section in inches by the number of columns 
and divide by the constant 20. The result is the square feet of 
radiating surface per section. The rule applies with least ac- 
curacy to the one-column radiators. 



108 



HEATING AND VENTLATION 



TABLE X. 



Dimensions and Surfaces of Radiators, per Section. 



Type of 
Radiator 


^1 

5 

8 

^% 

11 

8 
4 

7K 

12^ 

3^ 


11 

5 CO 

3 

3 

3 

3^ 

3 

3 

1^8 

2 






Radiator 


Hei 


ghts. 






45" 

5 

6 

10 


38" 

3 
4 
5 

8 


32" 

2H 

^^ 
4K 
6>^ 


26" 
2 

3K 
5 


23" 

P/3 

2>i 
.... 


22" 
3 


20" 

2 

6 


18" 


16" 


14" 


lOol.O. I 

2 Ool n T 










3 Ool. O.I 

4 0ol. 0. I 

Flue Wide.... 
Flue Narrow 

1 Ool. Press... 

2 Ool. Press . . 

3 Ool. Press . . 
1 Ool. Wall 


2K 
3 

5/3 


4% 


4 


.... 


7 
4 


5M 
5K 


4>^ 

2^ 
4% 










.... 


1 
2 

3^2 


1 




l>i 
2V4 


Pressed 

















76. Hot Water Heaters: — Heaters for supplying the hot 
water to a heating system may be divided into three classes: 
— the round vertical, for comparatively small installations; 
the sectional, for plants of medium size; and the water tube 
or fire tube heater with brick setting for the larger in- 
stallations and for central station work. The round and 
sectional types usually have a ratio between grate and 
heating surface of 1 to 20, while the water tube or fire tube 
heater will have, as an average, 1 to 40. Many different 
arrangements of heating surface are in use to-day, every 
manufacturer having a product of particular merit. Trade 
catalogs supply the most up-to-date literature on this 
subject, but cuts of each of the types mentioned above may 
be found in Fig. 55. 

77. Steam Boilers: — The products of many manufac- 
turers show but little difference between the hot water 
heater and the steam boiler. The latter is usually supplied 
with a somewhat larger dome to give greater steam stor- 
age capacity. For heating purposes, steam boilers fall 
into the same three classes as mentioned under water heat- 



HOT WATER AND STEAM HEATING 



109 



ers, having" about the same ratio of heating* surface to g-rate 
surface. With the steam boiler generating steam at 
5 pounds gage, the temperature on one side of tlie heating 
surface is about 227 degrees, while in a water heater tlie 
temperature on the same side is about 180 degrees. Hence, 
with the sam.e temperature of the burning gases, tlie tem- 
perature difference is g-reater in a water heater tlian in a 




Round Under- Feed 



Sectional Top Feed 




Fire Tube Type 
Fig. 55. 



110 



HEATING AND VENTILATION 



boiler, resulting in a more rapid transfer of heat, and a 
correspondingly greater efficiency. 

78. Combination Systems: — Combination systems are 
frequently used, principally the one which combines warm 
air heating with either steam or hot water. For such a 
system there is needed a combination heater, as shown in 
Fig. 20. It consists essentially of a furnace for supplying 
warm air to some rooms, the downstairs of a residence for 
instance, and contains also a coil for furnishing hot water 
to radiators located in other rooms, say, on the upper floors, 
or in places where it would be difficult for air to be de- 
livered. Considerable difficulty has been encountered in 
properly proportioning the heating surface of the furnace 
to that of the hot water heater, and the systems have not 
come into general use. 

79. Fittings: — Common and Special: — Couplings, elbows 
and tees, especially for hot water work, should be so formed 
as to give a free and easy sweep to the contents. It is 
highly desirable in hot water work to use pipe bends of a 





Fig. 56. 

radius of about five pipe diameters, instead of the common 
elbow. In either case all pipe ends should be carefully 
reamed of the cutting burr before assembling. This is 
most important, as the cutting burr is sometimes heavy 
enough to reduce the area of the pipe by one-half, thus 
creating serious eddy currents, especially at the elbows. 
If the single main hot water system be installed, great 
care should be used to plan the mains in the shortest and 
most direct routes, and the special fittings described and 
shown in Art. 65 should be used. 

Eccentric reducing /fittings are often of value in avoiding 
pockets in steam lines. Fig. 56 shows types of these, which 
should always be used wihen, by reduction or otherwise, a 



HOT WATER AND STEAM HEATING 



111 



horizontal steam pipe would present a pocket for the col- 
lection of condensation with its resultant water hammer. 

Valves for either steam or hot water should be of the 
g-ate pattern rather than the globe pattern. The latter is 
objectionable in hot water systems because of the resistance 
offered the stream of water, due to the fact that the axis 
of the valve seat opening is perpendicular to the axis of 
the pipe. The globe valve is objectionable in some 
steam lines because of the fact that in a horizontal run 
of pipe it forms very readily a pocket for the collection 
of condensation, thus often producing a source of water 
hammer. In every way gate valves are preferable, for, as 
shown in Pig. 57, they present a free opening -without turns. 

The same caution applies 
in the use of check valves. 
Swing checks should al- 
ways be specified rather 
than lift checks, for the 
former offer much less re- 
sistance to the passage of 
the hot water, or the 
steam and condensation, as 
the case may be. Fig. 58 
shows a lift check and a 
■^^^* • swing check. 

To avoid the annoyance so often experienced by leaky 
packing around valve stems, there have been designed and 










Fig. 58. 



placed on the market various forms of packless valves. 
These are to be especially recommended for vacuum work, 
as the old style valve with its packed stem Is, perhaps, the 
cause of more failures of vacuum systems than any other 
one item. Fig. 59 shows a section of this type of valve using 



112 



HEATING AND VENTILATION 



the diaphrag-ni as the flexible wall. All 
packless valves will be found to use a dia- 
phragm of one form or another. 

Quick-opening Valves, or butterfly valves, 
are much used on hot v/ater radiators; one- 
quarter turn of the wheel or handle serves 
to open these full and, when closed, they 
are so arranged that a small hole through 
IFlg". 59. the valve permits just enough leakage to 

keep the radiator from freezing. Special radiator valves for 
steam may also be obtained. 

Air valves have a most important function to discharge. 
As the air accumulates above the water or steam in the 





radiators, its removal becomes absolutely necessary, if all 
of the radiating surface is to remain effectual. For this 
purpose small hand valves or pet cocks, Fig. 60, are in- 
serted near the top of the end section in all hot water 
work; and either these same valves or automatic ones are 
inserted for steam work. Valves are not as essential on 
two-pipe steami systems as on water or single-pipe steam 
systems, yet are generally used. For steam the air valve 
should be about one-third the radiator height from the top. 

Fig. 61 shows a common type 
of automatic air valve using the 
principle of the expansion stem. As 
long as the air flows around the 
stem and exhausts, the stem re- 
mains contracted, and the needle 
valve open; but when the hot steam 
enters and flows past the expansion 
stem, it lengthens sufficiently to close the needle valve. In 
other forms of air valves the heat of the steam closes the 
needle valve by the expansion of a volatile liquid in a small 
closed retainer. In still other forms the lower part of the 
valve casing is filled with water of condensation upon 
which floats an inverted cup, having air entrapped withUa. 




Fig. 



HOT WATER AND STEAM HEATING 



113 



This cup carries the needle of the valve at its upper ex- 
tremity, the heat of the steam expanding the air sufficiently 
to raise the cup and close the valve. Where the system is de- 
signed to act as a gravity installation, special air valves must 
be used which will not allow air to enter at any time. Pig. 
62 shows a type of automatic valve designed to accommo- 
date larger volumes of air with promptness, 
as when a long steam main or large trap is 
to be vented. This type employs a long cen- 
tral tube, as shown, which carries at the top 
the valve seat of the needle valve. The 
needle itself is carried by the two side rods. 
As long as the air flows up through the 
centra.1 pipe, the needle valve will remain 
open; but when hot steam enters the tube, 
it expands, and carries the valve seat up- 
ward against the needle, thus closing the 
yalve. The size and strength of parts makes 
this form a very reliable one. 
The expansion tank. Fig. 63, for a hot wat- 
er system is often located in the bath room or 
closet near the bath room and its overflow 
connected to proper drainage. It should be 
at least 2 feet above the highest radiator. 
The connection to the heating system mains 
is most often by a branch from the nearest 
radiator riser, or it may have an independ- 
ent riser from the basement flow main. The 
capacity of the tank is usually taken at 
about one-twentieth of the volume of the 
entire system, or a more easily applied rule 
is to divide the total radiation 'by 40 to obtain the 
See Table 39, Appendix. 




'Fig. 62. 
capacity of the tank in gallons. 




Fig, 63. 



CHAPTER VIII. 



HOT WATER AND STEAM HEATING. 



PRINCIPLES OF THE DESIGN, WITH APPLICATION. 

In a hot water or steam system, the first important 
item to be determined by calculation is the amount of 
radiation, in square feet, to be installed in each room. 
Nearly all other items, such as pipe sizes, boiler size, grat© 
area, etc., are estimated with relation to this total radia- 
tion to be supplied. The correct determination, then, of 
the square feet of radiation in these systems is all-im- 
portant. 

80. Calcnlation of Radiator Surface: — rConsidering the 
standard room of Chapter III, where the heat loss was de- 
termined to be 14000 B. t. u. per hour on a zero day, the 
problem is to find what amount of surface and what size of 
radiator will deliver 14000 B. t. u. per hour to the room, 
under the conditions as given. Experiments by numerous 
careful investigators have shown that the ordinary cast iron 
radiator, located within the room and surrounded with com- 
paratively still air, gives ofC heat at the rate of 1.7 B. t. u. 
(1.6 to 1.8, or 1.7 average) per square foot per degree 
difference between the temperature of the surrounding air 
and the average temperature of the heating medium, per 
hour. This is called the rate of transmission. With hot 
water the average conditions within the radiator have 
been found to be as follows: temperature of the water en- 
te.ring the radiator 180 degree.s ; leaving the radiator 160 
degrees; hence, the average temperature at which the in- 
terior of the radiator is maintained is 170 degrees. Since, 
in this country, the standard room temperature is 70 de- 
grees, and, for hot water, the "degree difference" is 170 — 
70 = 100, then a hot water radiator will give off under 
standard conditions 1.7 X 100 = 170 B. t. u. per sq. ft. per hour. 
The temperature within a steam radiator carrying steam at 
pressures varying between 2 and 5 pounds gage is usually 
taken at 220 degrees, and the total transmission is approx- 
imately 1.7 X (220 — 70) = 255 B. t. u. per square foot per 



HOT WATER AND STEAM HEATING 115 

hour. The g-eneral formula for the square feet of radiation, 
then, is 

22 — Total B. t. u. lost from the room per hour 

1.7 (Temp. diff. between inside and outside of rad.) 

For hot water, direct radiation heating", this becomes, to the 

nearest thousandth 

H 
Rw = = .006 H (30) 

1.7 (170 — 70) 

For steam, direct radiation 

H 

Bs = = .004 H (31) 

1.7 (220 — 70) 

Rule. — To find the square feet of radiation for any room divide 
the calculated heat loss in B. t. u. per hour by the quantity 1.7 
times the difference in temperature detween the inside and the out- 
side of the radiator. 

It will be noticed from (30) and (31) that Rio = 1.5 Rs which 
accounts for the practice that some people have of finding 
all radiation as though it were steam, and then, when hot 
water radiation is desired, adding 50 per cent, to this 
amount. 

Application. — From the standard room under considera- 
tion, formula 30 gives Riv = .006 X 14000 = 84 square feet 
of radiator surface for hot water; and formula 31 gives Rs 
— .004 X 14000 = 56 square feet of radiator surface for 
steam. From these values the number of sections of a giv- 
en type of radiator can be determined by dividing by the 
area of one section, as explained in the preceding chapter. 
The length of the radiator may also be found from this 
same table, by noting the thickness of the section^, and 
multiplying by their number. 

Formulas 30 and 31 give the standard ratios be- 
tween the heat loss and direct radiation. If, however, the 
radiation is installed as direct -indirect, it is quite common 
practice to increase the amount of direct radiation by 25 
per cent, to allow for the ventilation losses. On this basis 
formulas 30 and 31 become, respectively, 

Rw = .0075 H (32) 

Rs = .005 H (33) 

Duct sizes for properly accommodating the air in 
direct-indirect heating may be taken from the following: 



116 HEATING AND VENTILATION' 

To oMain the duct area in square inches, multiply the square feet 
of radiation "by .75 to 1 for steam, and by .5 to .75 for hot water, 
To obtain the amounf" of air lohich may be expected to enter and 
pass through the radiator into the room, multiply the square feet 
of radiation by 100 for steam, or by 75 for hot water. This gives 
the cubic feet of air entering* per hour. 

Again, if the radiation is installed as purely indirect, 
yet not as a plenum system, it is common to increase the 
amount of direct radiation by 50 per cent. Now formulas 30 and 
31 become, respectively, 

Rxo — .009 H (34)-a 

Rs = .006 H (34)-b 

For proportioning- the duct sizes in indirect heating 
use the following table. To obtain the duct area in square 
inches, multiply the square feet of radiation installed by 

Steam Hot Water 

First Floor 1.5 to 2.0 1.0 to 1.33 

Second Floor 1.0 to 1.25 .66 to .83 

Other Floors .9 to 1.0 . 6 to .66 

Vent ducts, where provided, are usually taken .8 of the 
area of supply ducts. Also, for finding the amount of air in 
cubic feet, which may be reasonably expected to enter 
under these conditions. Carpenter gives the following: 
Multiply the square feet of indirect radiation by 



First Foor 
Second P loor 
Other Floors 

If this amount of air is insuflicient for the desired degree 
of ventilation, more air must be brought in by correspond- 
ingly larger ducts, and for each 300 cubic feet additional 
with steam, or each 200 cubic feet additional with hot 
water, add one square foot to the radiation surface. 

A steam sj^stem may be installed to work at any pres- 
sure, from a vacuum of, say, 10 pounds absolute, to as hig-h 
a pressure as 75 pounds absolute. To calculate the prop- 
er radiation for any of these conditions use formula 31 or 
its derivatives, and substitute the proper steam tempera- 
ture in place of 220 degrees. 

In like manner, to find the amount of hot water radi- 
ation for any other averag-e temperatures of the water 



Steam 


Hot Water 


200 


150 


170 


130 


150 


115 



HOT WATER AND STEAM HEATING 117 

than the one given, merely substitute the desired average 
temperature in the place of 170. One point should be re- 
membered, the maximum drop in temperature as the water 
passes through the heater will seldom be more than 20 
degrees, even under severe conditions. More often it will 
be less, but this value is used in calculations. Again, the 
temperature of the entering water may be at the boiling 
point, if necessary, thus causing each square foot of sur- 
face to be more efficient and consequently reducing the to- 
tal radiation in the room. To illustrate, try formula 30 
with a drop in temperature from 210 to 190 degrees and find 
64 square feet of radiator surface for this room. Since a 
radiator always becomes less efficient from continued use, it 
is best to design a system with a lower temperature as 
given in the formula, and then, if necessary under stress 
of conditions, this system may be increased in capacity by 
increasing the water temperature up to the boiling point. 
81. Empirical Formulas: — All of the above formulas may 
be considered as rational and checked by years of experience 
and application. Many empirical formulas have been de- 
vised in an attempt to simplify, but the results are always 
so untrustworthy that the rules are worthless unless used 
with that discretion which comes only after years of prac- 
tical experience. Many of these rules are based on the 
cubic feet of volume heated, without any other allowance, 
these being given anywhere from one square foot of steam 
surface per 30 cubic feet of space, to one square foot to 
100 cubic feet. The extreme variation itself shows the un- 
reliableness of this method, and under no conditions should 
it be used for proportioning radiating surface. Various 
central heating companies, and others, proportion radia- 
tors for their plants according to their own formulas, 
among which the following may be noted. 

G W G G W G 

(a) Rw = 1 1 Rs = 1 h 

2 10 60 2 10 200 

2 

(b) J?«, = G 4- .05 W -f .01 Rs =— (G + .05 W + .01 C) 

3 

(c) Rw = .75 Gf -f .10 W -}- .01 G Rs = .^ G + .0^ W -\- .005 G 
It is evident that these are really simplified forms of Car- 
penter's original formula. When applied to the sitting 
room, where Carpenter's formula gave, for hot water and 
steam, 84 square feet and 56 square feet, respectively, (a) 



118 HEATING AND VENTILATION 

g-ives 85.5 and 63, (b) gives 75 and 50, and (c) gives 82.5 
and 46 respectively. 

Another approximate rule devised by John H. Mills 
ani still used to some extent is "Allow 1 square foot of 
steam radiation for every 200 cubic feet of volume, 1 square 
foot for every 20 square feet of exposed wall and 1 square 
foot for every 2 square feet of exposed glass." Applying 
this to the standard room, it gives 9.75 + 13.25 + IS = 41 
square feet of steam radiation as against 56 square feet 
by rational formula. This shows a considerable difference 
from the rules preceding. 

82. Greenhouse Radiation: — The problem of properly 
proportioning greenhouse radiation is considered, by some, 
of such special nature as to justify the use of empirical 
formulas. The fact that the glass area is so large compared 
to the wall area and the volume, combined with the fact 
that the head of water in the system is small and that the 
radiation surface is usually built up as coils from 1^/4, 1^^ or 
2 inch wrought iron pipe, gives rise to a problem that differs 
essentially from that of a room of ordinary construction. It 
is not surprising, therefore, to find a great variety of empir- 
ical formulas designed exclusively for this work. Whatever 
merit these may ^ ave, they do not give the assurance that 
comes from the application of rational formulas. It is always 
best to use rational formulas first and then check by the 
various empirical methods. 

Formulas 30 and 31, stated in Art. SO, when properly 
modified, are applicable to greenhouses and give very re- 
liable results. As stated above, the radiating surface Is 
usually that of wrought iron pipes htang below the flower 
benches or along the side walls below the glass. The trans- 
mission constant, K, for wrought iron or mild steel is 2.0 to 
2.2 B. t. u. per square foot per degree difference per hour, 
making the total transmission per square foot of coil surface 
per hour about 2(170 — 70) = 200 for hot water, and 2(220 
— 70) = 300 for steam. These values may be safely used. 
The only necessary modification of the two formulas men- 
tioned, consists in replacing the constant 1.7 by 2, giving 
for 7wt water jj 

Rw — = .005 n (35)-a 

2(170 — 70) 
And for steam 

^' = 2(220-70) = ■'''' " ^''^■'^ 



HOT WATER AND STEAM HEATING 



119 



If, however, the highest temperature at which it is desirable 
to maintain the house in zero weather is other than 70 de- 
grees, this temperature should be used instead of 70. 

In a g-reenhouse there is very little circulation of air, 
hence the heat loss, H, would be found from the equivalent 
glass area i. e., {G -\- .25 TF). Formulas 35-a and & would 
then reduce to i?.r = .35 (G + .25 TT) and Rs — .23 (G + .25 TF). 
It is noticed that these values give about one square foot of 
II. W. radiation to 2.S square feet of equivalent glass area, and 
one square foot of steam radiation to 4.4 square feet of equivalent 
glass area as approximate rules. These figures should Itc eonsidered 
a minimum. 

Empirical rules for greenhouse radiation, quoted by 
many firms dealing in the apparatus, are usually given in 
the terms of the number of square feet of glass surface 
heated by one lineal foot of 1% inch pipe. A very commonly 
quoted and accepted rule is, one foot of lH inch pipe to 
every 2^/4 square feet of glass, for steam; or, one foot of 
1% inch pipe to every 1% square feet of glass, for hot water, 
when the interior of the house is 70 degrees in zero weather. 
Table XI, taken from the Model Boiler Manual, shows 
the amount of surface for different interior temperatures 
and different temperatures of the heating medium. 

In general, it may be said that in greenhouse heating, 
great care should be used in the rating and the selection 




RISE F( 

WATER OR STEAM 



Fig. 64. 



of the boilers or heaters. It is well to remember that the 
severe service demanded by a sudden change in the weather 
is much more difficult to meet in greenhouses than in ordin- 
ary structures, and that a liberal reserve in boiler capacity 
is highly desirable. 

If any greenhouse under consideration can be heated 
from some central plant where the heat will be continuous 
throughout the night with a man in charge at all times, 



120 



HEATING AND VENTILATION 



then steam is very desirable because of the reduced amount 
of heating surface necessary. If, however, in cold weather 
the steam pressure to be allowed to drop during the night- 
time, then hot water should be used. This permits a better 
circulation of heat throughout the greenhouse during the 
night. The same rules apply in running the mains and 
risers as would apply in the ordinary hot water and steam 
systems. In greenhouse work the head of water is very 
low and this makes the circulation rather sluggish but with 
sufficient pipe area and a minimum friction a hot water 
system may be used with satisfaction. In some houses the 
coils are run along the wall below the glass and supported 
on wall brackets, in others they are run underneath the 
benches and supported from the benches with hangers, 
while in greenhouses with very large exposure there are 
sometimes required both wall and bench coils. In all of 
these piping layouts it is necessary that • a good rise and 
fall be given to the pipes. Fig. 64 shows two systems of 
pipe connections, one where the steam or flow enters the 
coils from above the benches and the other where it enters 
from below, the return in each case being at the lowest 
point. These bench coils could be run along the wall with 
equal satisfaction. 

TABLE XI. 



© 3Q 


Temperature of Water in Heating Pipes 


Steam 


C 


liOO 


I6OO 


I8OO 


200'^ 


Three lbs. 










Pressure 


Square feet of glass and its equivalent pro 


portioned to 


one square foot of surface in heating pipes 


3 or radiator 


40O 


4.33 


5.25 


6 66 


7.69 


8. 


7.5 


450 


3. 63 


4.65 


5 55 


6.66 


7.5 


6.75 


500 


8 07 


3.92 


4 76 


5.71 


7. 


6.0 


650 


2 63 


3.39 


4.16 


5. 


6.5 


5.5 


6OO 


2.19 


2.89 


3.63 


4.33 


6. 


50 


650 


1.86 


2.53 


3 22 


3.84 


5.5 


4.5 


700 


1.58 


2.19 


2.81 


3 44 


5. 


4,25 


750 


1.37 


1.92 


2 5 


3.07 


4.5 


4.0 


8OO 


1.16 


1.63 


2.17 


2 73 


4. 


8.75 


850 


.99 


1.42 


1.92 


2.46 


3.5 


3.5 



This table is computed for zero weather; for lower 
temperatures add 1^ per cent, for each degree below zero. 



HOT WATER AND STEAM HEATING 121^ 

The last column in Table XI has been calculated from 
formula 35-b and added for purpose of comparison. 

Application. — Given an even span greenhouse 25 ft. wide, 
100 ft. long and 5 ft. from ground to eaves of roof, having 
slope of roof with horizontal 35°. Ends to be glass above 
the eaves line. What amount of hot water radiation with 
water at 170° and what amount of low pressure steam radia- 
tion would be installed? 

Length of slope of roof = 12.5 ~- cos. 35* = 15.25. 

Area of glass = 15.25 X 100 X 2 + 2 X 12.5 X 8.8 = 3270 
sq. ft. 

Area of wall = 5X100X2 + 5X25X2 = 1250 sq. ft. 

Glass equivalent = 3270 + .25 X 1250 = 3582.5 sq. ft. 

Rw= .35 X 3582.5 = 1253.8 sq. ft. 

ats = .23 X 3582.5 = 824. * ,sq. ft. 

From Table XI. 

Rxo= 3582.5 -^ 2.5 = 1433 sq. ft. 

Rs = 3582.5 -^ 5 = 716. >sq. ft. 

*Check with last column of Table XT. 

83. The Determination of Pipe Sizes :r— The theoretical 
determination of pipe sizes in. hot water and steam systems 
has always been more or less unsatisfactory, first, because 
of the complicated nature of the problem when all points 
having a bearing upon the subject are considered, and 
second, because it is almost an impossibility to even ap- 
proximate the friction offered by different combinations and 
conditions of piping. The following rather brief analysis 
gives a theoretical method for determining pipe sizes where 
friction is not considered. 

In a hot water system let the temperatures of the water 
entering and leaving the radiator be, respectively, 180 
and 160 degrees; then it is evident that one pound of the 
water in passing through the radiator, gives off 20 B. t. u. 
Under these conditions the standard rooin would have 14000 -r- 
20 = 700 pounds of water passing through the radiator per 
hour. Converting this to gallons, it is found to be 84.03. 
But the radiation for this room was found to be 84 square 
feet. Therefore, it may be said that a hot water radiator 
unde-^ normal conditions of installation and under heavy 
service requires one gallon of water per square foot of sur- 
face per hour. Knowing the theoretical amount of water 
per hour, it remains only to obtain the theoretical speed 



122 HEATING AND VENTILATION 

at which it travels, due to unbalanced columns, to obtain 
finally, by division, the theoretical area of the pipe. 

Consider a radiator to be about 10 feet above the 
source of heat, and the temperature in the flow riser to be 
180 degrees and in the return riser 160 degrees, good values 
in practice. Now the heated water in the flow riser 
weighs 60.55 67 pounds per cubic foot, while that in the 
return riser weighs 60.9697 pounds per cubic foot. The mo- 



/ W — W \ 
V T7 + W / 



tive force is f = g ( ) where g is the acceleration 

V T7 + W / 

due to gravity, W is the specific gravity (weight) of the 
cooler column and W is the specific gravity (weight) of the 
warmer column. Substitute f for g in the velocity formula 



and obtain v = y/2fli and 



v=J 2glil ) (36) 

Inserting values TT, W and assuming 7i = 10 feet, we have 
V = V2 X 32.2 X 10 X .0034 = V 271896 ==1.47 feet per second. 
From this it has become a custom to speak of 1.5 feet per 
second or 5400 feet per hour, as the theoretical velocity of 
water in, say, a first floor riser, disregarding the effect of 
all friction and horizontal connections. Theoretical veloci- 
ties for any other height of column and for other temper- 
atures may be obtained in like manner. Continuing this 
special investigation and changing the 84 gallons per hour 
to cubic inches per hour by multiplying by 231, the internal 
pipe area may be obtained by dividing by the unit speed 
per hour which gives (84 X 231) ~ (5400 X 12) = .3 square 
inch. This corresponds to approximately a % inch pipe 
and without doubt, would supply the radiator if the sup- 
position of no frictional resistances could be realized. This 
ideal condition, of course, cannot be had, nor can the fric- 
tion in the average house heating plant be theoretically 
treated with any degree of satisfaction. Hence it is still 
the custom to use tables for the selection of pipe sizes, 
based upon what experience has shown to be good practice. 
Such tables, from various authorities, may be found in the 
Appendix. It is safe to say that one should never use any- 
thing smaller than a 1 inch pipe in low pressure hot water 
work. 

With steam systems, where the heating medium is a vapor, 



HOT WATER AND STEAM HEATING 123 

and subject in a lesser degree to friction, the discrepancy 
between the theoretical and the practical sizes of a pipe 
is not so great as in hot water. Each pound of steam, in 
condensing, gives off approximately 1154 — 181 = 973 B. t. u. 
To supply the heat loss of the standard room, 14000 B, t. a. 
per hour, it would require 14.5 pounds of steam per hour. 
When it is remembered that the calculated surface of the 
direct steam radiator for this room was 56 square feet, it 
appears that a radiator, under stated conditions and under a 
heavy service, requires one-fourth of a pound of steam per square 
foot of surface per hour. This may be shown in another way: 
each square foot of steam radiation gives off 255 B. t. u. 
per hour; then, each square foot will condense 255 -r- 973 = 
.26 + pounds of steam per hour. 

Now the volume of the steam per pound at the usual 
steam heating pressure, 18 pounds absolute, is 21.17 cubic 
feet. Since the standard room radiator required 14.5 pounds 
per hour, it would, in that time, condense steam corres- 
ponding to a void of 21.17 X 14.5 = 307 cubic feet per hour. 
This is the volume of the steam required by the radiator, 
and, if the speed of the steam in the pipe lines be taken 
at 15 feet per second, or 54000 feet per hour, the area of 
the pipe would be 307 X 144 -r 54000, or .82 square inch, 
corresponding very closely to a 1 inch pipe. For a two- 
pipe system this would be considered good practice under 
average conditions; but in a one-pipe system, where the 
condensation is returned against the steam in the same 
pipe that feeds, a pipe one size larger would be taken. 

Table 35, Appendix, calculated from Unwin's formula, 
may be used in finding sizes and capacities of pipes carrying 
steam. In addition to this, Tables 31, 32, 33 and 34 give sizes 
that are recommended by experienced users. 

For a theoretical discussion of loss of head by friction 
in hot water and steam pipes, see Arts. 147 and 175. 

84. Grate Area: — To obtain the grate area for a direct 
radiation hot water or steam system by the B. t. u. method, 
the same analysis as found in Chapter IV may be applied. 
The total B. t. u. heat loss, H, is that calculated by the 
formula and does not include Hv, the heat loss due to ven- 
tilation, since with the direct hot water or steam system as 
usually installed no ventilation is provided. In any special 
case where ventilation is provided in excess, use H^ instead 
of H. The commercial rating of heaters and boilers is a 



124 HEATING AND VENTILATION 

subject each day receiving" greater attention at the hands 
of manufacturers; yet it is a subject where much uncer- 
tainty is felt to exist. Hence the recommendation, "Always 
check g-rate area by an actual calculation," rather than rely 
entirely upon the catalog ratings. 

85. Pitch of Mains: — The pitch of the mains Is quite as 
important in hot water as in steam work. This should be 
not less than 1 inch in 10 feet for hot water systems, and not 
less than 1 inch in 30 feet for steam systems. Greater 
pitches than these are desirable, but not always practic- 
able. In hot water plants the pitch of the basement mains, 
whether flow or return, is upward as these mains extend 
from the source of heat, that is, the highest point is the 
farthest from the heater. In steam plants the mains, under 
any condition of arrangement, always pitch downward 
in the direction of the flow of the condensation. 

86, liocation and Connection of Radiators: — In locat- 
ing" radiators, it is best to place them along the outside or 
the exposed walls. When allowable, under the windows 
seems to be a favorite position. Especially in building"s 
of several stories, the radiators should be arrang"ed, where 
possible, in tiers, one vertically above another, thus re- 
ducing" the number of and avoiding" the offsets in the risers. 
In the one-pipe system any number of radiators may be con- 
nected to the same riser. In the two-pipe system several 
radiators may have either a common flow riser, or a common 
return riser, but should never have both, either with hot 
water or with steam. 

The connections from the risers to the radiators should 
be slightly pitched for drainage and are usually run along 
the ceiling below the radiator connected. These connections 
should be at least two feet long to give that flexibility of 
connection to the radiator made necessary by the expan- 
sion and contraction of the long riser. Similarly, all risers 
should be connected to the mains in the basement by hori- 
zontals of about two feet to allow for the expansion and 
contraction of the mains. A system thus flexibly connected 
stands in much less dang-er of developing leaky joints than 
does one not so connected. For sizes of radiator connections 
see Table 29, Appendix. 



HOT WIATER AND STEAM HEATING 125 

87. General Application: — Figs. 65, 66 and 67 show the 
typical layout of a hot water plant. Due to the similarity be- 
tween hot water and steam installations, the former only will 
be designed complete. In attempting the layout of such a 
system, the very first thing to be done is to decide at what 
points in the rooms the radiators should be placed. This 
should be done in conjunction with the owner as he may 
have particular uses for certain spaces from which radia- 
tors are hence excluded. The first actual calculation should 
be the heat loss from each room, with the proper exposure 
losses, and the results should be tabulated as the first 
column of a table similar to Table XII. In the 
example here given, this loss is the same as, and taken 
from, the table of computations for the furnace work. Art. 
48, the house plans being identical. The second column 
of Table XII, as indicated, is the square feet of radiation; 
and since this is a hot water, direct radiation system, it 
is obtained by taking .006 of the items in the first column 
according to formula 30. Knowing this, a type and 
height of radiator can be selected, and the number of 
sections determined by Table X. Next obtain the lengths 
of radiators by multiplying the number of sections by the 
total thickness of the sections, as given in Table X, and 
determine whether or not the radiator of such a length 
will fit into the chosen space. If not, then a radiator of 
greater height and larger surface per section must be 
selected. Riser sizes and connections may be taken ac- 
cording to Tables 81 and 29 respectively. The column of 
Table XII headed "Radiators Installed" gives first the num- 
ber of sections; second, the height in inches; and third, the 
number of columns or type of the section. 

Locate radiators on the second floor and transfer the 
location of their riser positions to first floor plan, then to 
the basement plan. Locate radiators on the first floor and 
transfer their riser locations to the basement plan, which 
will then show, by small circles, the points at which all 
risers start upward. This arrangement will aid greatly in 
the planning of the basement mains. 

The keynotes in the layout of the basement mains 
should be simplicity and directness. If the riser positions 
show approximately an even distribution all around the 
basement, it may be advisable to run the mains in 



126 HEATING AND VENTILATION 

complete circuits around the basement. If, again, the 
riser positions show ag-greg-ation at two or three localities, 
then two or three mains running" directly to these localities 
would be most desirable. As an example, take the applica- 
tion shown here. The basement plan shows three clusters 
of riser ends, one under the kitchen, another under the 
study, and a third on the west side of the house. This 
condition immediately sug-g-ests three principal mains, as 
shown. The main toward the kitchen supplies the bath, 
chamber .4 and the kitchen, making a total of 131 square 
feet. Being- only about 13 feet long, it would readily carry 
this radiation if of 2 inch diameter. See Table 34, Appendix. 
The main to the study and the hall supplies chamber 1, the 
hall and the study, making* a total of 221 square feet, which 
can be carried by a 2^ inch pipe. The main to the west side 
of the house supplies chamber 2, chamber 3, the sitting room 
and the dining room, a total of 249 square feet, which would 
almost require a 3 inch main, according to the table, were 
it not for its comparatively short length. A 2^/^ inch pipe 
would amply supply this condition. 

In hot water work, as well as in steam, it is customary 
to take the connections to flow risers from the top of the 
mains, thus aiding the natural circulation. Fig. 35. If not 
taken directly from the top of the main, it is often taken at 
about 45 degrees from the top. This arrangement, with a 
short nipple, a 45 degree elbow, and the horizontal connec- 
tion about iy2 to 2 feet long, makes a joint of sufficient 
flexibility between the main and riser to avoid expansion 
troubles. 

In the selection of a heater or boiler much that has 
been said concerning furnaces applies. The heater or boiler 
should, above all, have ample grate area, checked on a B. 
t. u. basis, and should have a sufficient heating surface so 
designed that the heated gases from the fire impinge per- 
pendicularly upon it as often as may be without seriously 
reducing the draft. As shown by the total of the radiation 
column, a hot water boiler should be selected of such rated 
capacity as to include the loss from the mains and risers. 
Since this loss is usually taken from 20 to 30 per cent., de- 
pending upon the thoroughness with which the basement 
mains are insulated, the heater for this house should have 
a rated capacity of not ""ess than 720 square feet of radiation. 



HOT WATER AND STEAM HEATING 
TABLE XII. 



127 



Sitting R 

Dining R 

Study 

Kitchen 

Rec'p'n Hall 

Chamber 1 

Ohamber 2..., 

Ohamber 3 

Ohamber 4 

Bath 



b-'X 


o 


s^ 


w 


► 4) 


c«s. 


-1 




<D O 


oil 

84 


14000 


10800 


65 


13250 


80 


11900 


70 


14000 


84 


9400 


57 


9850 


60 


6600 


40 


5600 


35 


4400 


26 




601 



Radiators 
installed 



32-3 
•26-3 
14-3 
32-3 
32-3 
26-3 
26-3 
26-3 
26-3 
26-3 



14-44-3 
18-26-3 
20-14-F 
8 -45-4 
14-44-3 
16-26-3 
16-26-3 
12-26-3 
12-26-3 
7-26-3 



Lengths 
of rad'or 
installed 


Riser 
sizes 


1 

(A 
CA 
0) 




o 


a 


34 


42 


VA 


V-A 


32 


54 


VA 


Ik 


72 


60 


\V2 


P/2 


26 


24 


I'A 


1^2 


34 


42 


IM 


m 


30 


48 


IK 


VA 


30 


48 


1% 


VA 


23 


36 


1 


1 


23 


36 


1 


1 


14 


21 


1 


1 



ON 



IK 
IK 
IK 
1^ 

VA 

VA 

VA 

1 

1 

1 



128 



HEATING AND VENTILATION 



27 — 6^ 




FOUNDATION PLAN. 
Ceiling 6\ 

Fig. 65. 



HOT WATER AND STEAM HEATING 



129 




FIRST FLOOR PLAN. 
Ceiling 10'. 



Fig. 66. 



130 



HEATING AND VENTILATION 



a-iTZ-ft'oV l/\ 



iL^ia".34" 




SECOND FLOOR PLAN. 

Ceiling 9'. 



Fig. 67. 



HOT WATER AND STEAM HEATING 



131 



I2-2S-3 7-26-5 



Exp.TonK. 




J6-26-3 



IA'4^-3 



16-26-3 
MAIN AND RISER LAYOUT. 

Fig-. 67a. 



88. Insnlatins Steam Pipes: — In all heating systems, 
pipes carrying steam or water should be insulated to protect 
from heat losses, unless these pipes are to serve as radiating 
surfaces. In a large number of plants the heat lost through 
these unprotected surfaces, if saved, would soon pay for first 
Class insulation. The heat transmitted to still air through 



132 HEATING AND VENTILATION 

one square foot of the average wrought iron pipe is from 2 
to 2.2 B. t. u. per hour, per degree difference of temperature 
between the inside and the outside of the pipe. Assuming 
the minimum value, and also that the pipe is fairly well 
protected from air currents, the heat loss is, with steam at 
100 pounds gage and 80 degrees temperature af the air, 
(338 — 80) X 2 = 516 B. t. u. per hour. With steam at 50, 25 
and 10 pounds gage respectively this will be 436, 374 and 320 
B. t. u. If the pipe were located in moving air, this loss would 
be much increased. It is safe to say that the average low pres- 
sure steam pipe, when unprotected, will lose between 350 and 
400 B. t. u. per square foot per hour. Taking the average of 
these two values and applying it to a six inch pipe 100 feet 
in length, for a period of 240 days at 20 hours a day, we have 
a heat loss of 171 X 375 X 240 X 20 = 307800000 B. t. u. With 
coal at 13000 B. t. u. per pound and a furnace efficiency of 60 
per cent, this will be equivalent to 39461 pounds of coal, 
which at $2.00 per ton will amount to $39.46. From tests 
that have been run on the best grades of pipe insulation, it is 
shown that 80 to 85 per cent, of this heat loss could be 
saved. Taking the lower value we would have a financial 
saving of $31.56 where the covering is used. Now if a good 
grade of pipe covering, installed on the pipe, is worth $35.00, 
the saving in one year's time would nearly pay for the 
covering. 

To be effective, insulation should be porous but should 
be protected from air circulation. Sm.all voids filled with 
still air make the best insulating material. Hence, hair 
felt, mineral wool, eiderdown and other loosely woven ma- 
terials are very efficient. Some of these materials, however, 
disintegrate after a time and fall to the bottom of the pipe, 
leaving the upper part of the : ipe comparatively free. Many 
patented coverings have good insulating qualities as well as 
permanency. Most patented coverings are one inch in thick- 
ness and may or may not fit closely to the pipe. A good ar- 
rangement is to select a covering one size larger than the 
pipe and set this off from the pipe by spacer rings. This 
air space between the pipe and the patented covering is a 
good insulator itself. Table 45, Appendix, gives the 
results of a series of experiments on pipe covering, obtained 
at Cornell University under the direction of Professor Car- 
penter. These values are probably as nearly standard as 
may be had. (See Art. 138 for conduits.) 



HOT WATER AND STEAM HEATING 



133 



89. Water Hammer: — 'When steam is admitted to a cold 
pipe, or to a pipe that is full of water, it is suddenly con- 
densed and causes a sharp cracking" noise. The concussion 
produced by this condensation may become so severe as to 
crack the fitting's and open up the joints. The noise is due to 
a sudden rush of water in an endeavor to fill the vacuum 
produced by the condensed steam. Steam at atmiospheric 
pressure occupies 1644 times the volume of the water that 
formed it, hence, by suddenly condensing it, a very hlg^h 
vacuum may be produced. This action causes a relatively 
high velocity in any body of water adjacent to it. The 
worst condition is found when a quantity of steam enters 
a pipe filled with water. Condensation suddenly takes place 
and the two bodies of water come together with high ve- 
locity causing severe concussion. Steam should always be 
admitted to a cold pipe, or to one filled with water, very 
slowly. 

90, Retiirning" fhe Water of Condensation, in a L.otf 
Pressure Steam Heating System, to the Boiler: — In re- 





Fig. 68. 



Fig. 69. 



turning the water of condensation to the boiler four methods 
are in use; gravity, steam traps, steam loops and steam or 
electric pumps. The gravity system is the simplest and is used 
in all cases where the radiation is above the level of the 
boiler and where the boiler pressure is used in the mains. 
In a gravity return, no special valves or fittings are neces- 
sary, but a free path with the least amount of friction in It 
is provided between the radiators and a point on the boiler 
below the water line. No traps of any kind should be 
placed in this return circuit. 

All radiation should be placed at least 18 inches above 
the water line of the boiler to insure that the water will 
not back up in the return line and flood the lower radiators. 



134 HEATING AND VENTILATION 

This flooding- is usually the result of a restricted steam main. 
When the radiation is below the water line, or where the 
pressure in the mains is less than that in the boiler, some 
form of steam-trap or motor pump must be put in with special 
provision for returning- this water to the boiler. Two kinds 
of traps may be had, low pressure and high pressure. The 
first is well represented by the bucket trap, Fig. 68, and the 
second, by the Bundy trap. Fig. 69. The action of these traps 
is as follows. Bucket trap. — Water enters at D and collects 
around the bucket, which is buoyed up against the valve. 
The water collects and overflows the bucket until the com- 
bined weight of the water and bucket overbalances the 
buoyancy of the water. The bucket then drops and the 
steam pressure upon the inside, acting upon the surface of 
the water, forces it out through the valve and central stem 
to the outlet B. When a certain amount of this water has 
been ejected, the bucket again rises and closes the valve. 
This action is continuous. Bundy trap. — Water enters at D 
through the central stem and collects in the bowl A, which 
is held in its upper position by a balanced weight. When 
the water collects in the bowl sufficiently to lift the weight, 
the bowl drops, the valve E opens, and steam is admitted 
to the bowl, thus forcing the water out through the curved 
pipe and the valve E. This action is continuous. 

Each trap is capable of lifting the water approximately 
2.4 feet for each pound of differential pressure. . Thus, for a 
pressure of 5 pounds gage within the boiler and 2 pounds 
gage on the return, the water may be lifted 7 feet above 
the trap, or say, to the top of an ordinary boiler. This is not 
sufficient, however, to admit the water into the boiler 
ag-ainst the pressure of the steam. A receiver should be 
placed here to catch the water from the separating trap, 
and deliver it to a second trap above the boiler which, in, 
turn, feeds the boiler. Live steam is piped from the boiler 
to each trap, but the steam supply to the lower trap is, 
throttled, to give only enough pressure to lift the water 
into the receiver. A system connected up in this way is 
shown in Fig 70. Traps which receive the water of con- 
densation for the purpose of feeding the boiler are called 
return traps and sometimes work under a higher pressure 
of steam than the separating traps. Many different kinds 
of traps are in general use but these will illustrate the 
principle of returning the condensation to the boiler. 



HOT WATER AND STEAM HEATING 



135 



mp 




VtNTPlPE TO ASH PIT 

Fig-. 70. 



A very simple arrange- 
ment, and yet a very difficult 
one to operate satisfactorily, 
is by the use of the steam loop. 
Fig". 71. The water of con- 
densation from the radiators 
drains to the receiver A, 
which is in direct communi- 
cation with the riser B. The 
drop leg" D, being in com- 
munication with the boiler 
through a check valve which 
opens toward the boiler at 
the lowest point, is filled 
with water to the point X, 
■sufficiently high above the 
water line of the boiler that 
the static head balances the differential pressure between the 
steam in the boiler and that in the condenser. The horizon- 
tal run of pipe G serves as a condenser ?-nd, in producing a 
partial vacuum, lifts the water from the receiver. This 
water is not lifted as a solid body, but as s-^ugs of water 
interspersed with quantities of steam and vapor The water 
in A is at or near the boiling point and the reduced pressure 
in B reevaporates a portion of it which, in rising a? a 
vapor, assists in carrying the rest of the water over the 
goose-neck. When the condensation in D rises above the 
point X, the static pressure overbalances the differential 
steam pressure, and water is fed to the boiler through the 
check. 

To find the location of the point X, above the water line 
in the boiler, the following will illustrate. Let the pres- 
sures in the boiler, condenser and receiver be respectively 
5, 2 and 4 pounds gage, then the differential pressure between 
the boiler and condenser is 3 pounds per square inch. If the 
weight of one cubic foot of water at 212 degrees is 59.76 
pounds, then the pressure is .42 pounds per square inch for 
each foot in height. Stated in other words, one pound dif- 
ferential pressure will sustain 2.4 feet of water. With a 
pressure difference of 3 pounds, this gives 3 -^ .42 = 7.2 
feet from the water level in the boiler to the point X, not 
taking into account the friction of the piping and check 
which would vary from 10 to 30 per cent. Assuming this 



136 



HEATING AND VENTILATION 



friction to be 20 per cent, we have 7.2 ^ .80 = 9 feet of head 
to produce motion of the water. 

The length of the riser pipe B and its diameter, depend 
upon the differential pressure between the condenser and 
the receiver, and upon the rapidity of condensation in the 
horizontal. 

With a differential pressure of 2 pounds this would sus- 
pend 2 X 2.4 = 4.8 feet of solid water. The specific gravity, 
however, of the mixture in this pipe is much less than that 
of solid water. For the sake of argument let this specific 
gravity be 20 per cent, of that of solid water, then we would 



AIR valve: 



goose: neck 




CONDENSER C 



- -¥c 



CHECK 



I 1 


II II 




— 


=^— 


— 


=-^^ 


^BOILER 


=_-^_= 


.S==^. 





= £7- 


— 


^ = 


■ — 


— — 



Fig. 71. 
have a possible lift, not including friction, of 5 X 4.8 = 24 
feet. This is 24 — 9 = 15 feet below the water level in the 
boiler. The diameter of the riser may vary for different 
plants, but for any given plant the range of diameters is 
very limited. These, as has been stated, are usually found 
by experiment. 

A drain cock should be placed in the receiver at the 
lowest point. When cold water has collected in the re- 
ceiver it is necessary to drain this water to the sewer before 
the loop will work. An air valve should be placed at the top 
of the goose-neck to draw off the air. If the horizontal pipe 
is filled with air, there will be no condensation and the loop 
will refuse to work. Never connect a steam loop to a boiler 



HOT WATER AND STEAM HEATING 



137 



in connection with a pump or any other boiler feeder. To 
determine whether a loop is working or not, place the hand 
on the horizontal pipe. If this is cold it is not working. 

The last method mentioned for feeding condensation to 
the boiler was by the use of a steam or electric pump. The 
operation of the steam pump is fully discussed in Art. 92. 
An electric motor-pump with its receiver and pipe connec- 
tions is shown in Fig. 72. Its operation is very similar to 
that of the steam pump. When the returning condensation 

■ ^ — tu - 



/^ EQUALIZING 
^^ PIPE 




Fig. 72. 



fills the receiver to a certain point a float regulator starts 
the motor and pumps the water from the receiver to the 
boiler. W^hen the water level drops the operation is re- 
versed and the pump is automatically stopped. The motor 
pump is used .especially on low pressure heating systems 
Wihere the water of condensation from the coils and radia- 
tors drains below the boiler. If the boiler pressure were 
high then the ordinary steam pump would be used. Where 
the pressure within the boiler, however, is near that in the 
return main the operation of such a piece of apparatus is 
less expensive than that of the steam pump. 

91. Suggestions for Operating Hot Water Heaters and 
Steam Boilers: — Before firing up in the morning, examine 
the pressure gage to see if the system is full of water. If 
there be any doubt, inspect the water level in the expan- 
sion tank. If it is a steam system, examine the gage glass 
and try the cocks to see if there is sufficient water in the 
boiler. 



138 HEATING AND VENTILATION 

See that all valves on the water lines are open. On the 
steam system try the safety valve to make sure that it Is 
free. Also see if the pressure gage stands at zero. 

Clean the fire and sprinkle over it a small amount of 
fresh coal. 

Open up the drafts and v^hen the fire is burning well 
fill up with coal. 

In starting a fire under a cold boiler it should not be 
forced, but should warm up gradually. 

Hard coal may be thrown evenly over the fire. Soft coal 
should be banked in front on the grate, until the gases are 
driven off. It is then distributed back over the fire. 

The thickness of the fire will vary from four inches to 
one foot depending upon the draft and the kind of coal. 

Clean the fire when it has burned low, partially closing 
the drafts while cleaning. 

In a boiler or heater, using the water over continuously, 
there will be little need of cleaning out the inside. In a 
system using fresh water continuously, however, the boiler 
should be blown off and cleaned about once or twice a month. 
Never blow off a boiler while hot or under heavy pressure. 

In every system the heater or boiler should be thoroughly 
overhauled and cleaned before firing up in the fall. 

Keep the ash pit clean and protect the grates from burn- 
ing out. 

Keep the tubes and gas passages clean and free from soot. 

Inspect the pressure gage, glass gage, water cocks and 
thermometers frequently. 

In case of low water in a steam system, cover the fire 
with wet ashes or coal and close all the drafts. Do not 
open the safety valve. Do not feed water to the boiler. Do 
not draw the fire. Keep the conditions such as to avoid any 
sudden shock. After the steam pressure has dropped, draw 
the fire. 

Excessive pressure may be caused by the sticking of the 
safety valve in the steam system, or by the stoppage of the 
water line to the expansion tank in the hot water system. 
The safety valve should never be allowed to lime up, and the 
expansion tank should always be open to the heater and to 
the overflow. 

When leaving the fires for the night, push them to the 
rear of the grate and bank them aa stated in Art. 59. 



HOT WATER AND STEAM HEATING 139 

\ 
References on Hot Water and Steam. 

Technical Books. 

Snow, Principles of Heat., Chap. IX, X. I. C. S., Prin. of Heat, 
and Vent., p. 1185, 1091. Monroe, Steam Heat. & Vent., p. 13. 
Lawler, Hot Water Heating, p. 19. Carpenter, Heat. & Vent. Bldgs., 
pp. 150, 231. Thompson, House Heat, by Steam d Water, p. 15. 
Hubbard, Power, Heat. & Tent., pages 433, 464, 484, 505, 510. 

Technical Periodicals. 

Engineering News. Suggestions for Exh'st Steam Heat, 
Apr. 7, 1904, p. 332. An Improved Steam Heat. System, Ther- 
mograde System, July 23, 1903, p. 80. Factory System of the 
United Shoe Machinery Co., Y/. C. Snow, May 25, 1905, p. 537. 
Heating a Trolley Car Barn, J. I. Brewer, April 29, 1909, p. 
462. Engineering Review. Heat. & Vent, of the New Parental 
Home and School at Flushing, L. I., Jan. 1910, p. 48. A Hot 
Water System with Radiators and Boiler on the Same Level, 
J. P. Lisk, Aug. 1908, p. 34. A Hot Water Heat. System for 
a City Residence, J. P. Lisk, June 1909, p. 44. Hot Water 
Heat. Apparatus in Plymouth Church, Brooklyn, N. Y., Dec. 

1908, p. 19. Heat., Vent, and Temperature Regulation in the 
Measles Pavilion of the Kingston Ave. Hospital, Brooklyn, 
N. Y., Jan. 1910, p. 35. Heat, and Vent. Plant of the Boston 
Safe Deposit and Trust Company's Building, C. L. Hubbard, 
April 1910, p. 37. Heat, and Vent. Installation in the Burnet 
St. School, Newark, N. J., Jan. 1909, p. 20. A Unique Low 
Pressure Steam Heat. Apparatus, Feb. 1909, p. 38. Practical 
Points on Steam Heating (Direct Heating), C. L. Hubbard, 
Aug. 1908, p. 29. (Indirect Heat.), Sept. 1908, p. 19. (Exhaust 
Steam Heat.), Nov. 1908, p. 21. Steam Heating Systems, 
Wm. J. Baldwin, March 1905, p. 7. Machinery. Shop Heating 
by Direct Radiation, C. L. Hubbard, July 1910, p. 884. Sizes 
of Pipe Mains for Hot Water Heating, C. L. Hubbard, Sept. 

1909, p. 38. The Railway Review. Heating System of the Scrar^- 
ton St. Railway Shops, June 13, 1908, p. 480. Heating of 
Passenger Trains, May 23, 1908, p. 408. The Pennsylvania 
R. R. System of Heat, and Vent. Passenger Cars, Feb. 22, 1908, 
p. 157. Vent, and Heating of Coaches and Sleeping Cars, 
July 18, 1908, p. 586. Hot Water Heating Arrangements for 
Passenger Stations, Oct. 10, 1908, p. 829. Typical Heating 
Plants, Horace L. Wdnslow Co., June 18, 1910, p. 596. The 
Heating & Ventilating Magazine. Residence Heating by Direct 
and Indirect Hot T^^-ater, July 1905, p. 25. Carrying Capac- 
ities of Pipes in Low Pressure Steam Heating, Wm. Kent, 
Feb. 1907, p. 7. Standard Sizes of Steam Pipes, Jas. A. Don- 
nelly, Jan. 1907, p. 21. Formula for Pipe Sizes in Hot Water 
Heating, Oliver H. Schlemmer, Sept. 1907, p. 9. Coefficient 
of Transmission in Cast iron Radiation, John R. Allen, Aug. 
1908, p. 20. Relative Capacities of Pipes, John Jaeger, May 
1907, p. 1. Methods of Figuring Radiation, Gerard W. Stan- 
ton, Dec. 1907. p. 1. Computation of Radiating Surface, J. 
Byers Hol'brook, Nov. 1904, p 77. Coefficients of Heat Trans- 
mission, John R. Allen, July 1911. Domestic Engineering. A 
Practical Manual of Steam and Hot Water Heating, E. R. 
Pierce, (Series of Articles), Vol. 51, No. 2, April 9, 1910; Vol. 
53, No. 9, Nov. 26. 1910. Proportions and Power of Low 
Pressure Heating Boilers, Vol. 47, No. 11, June 12, 1909. p. 
319. How to Instaill and Cover a Steam or Hot Water Main, 
"Phoenix," Vol. 46, No. 10, March 6, 1909, p. 278. How to 



140 HEATING AND VENTILATION 

Secure Correct Pipe Sizes for Low Pressure Steam. Heating, 
E. K. Monroe, Vol. 45, No. 9, Nov. 28, 1908, p. 243. Rules for 
Proportioning- Indirect Heating- Plants, R. T. Crane, Vol. 49, 
No. 6, Nov. 6, 1909, p. 143. Trans, A. S. H. & V. E. Circulation 
of Hot Water, J. S. Brennan, Vol. XI, p. 93. Residence Heat- 
ing" by Direct and Indirect Hot Water, E. F. Capron, Vol. 
XI, p. 174. Standard Sizes of Steam Mains, J. A. Donnelly, 
Vol. XIII, p. 43. The Carrying- Capacity of Pipes in Low 
Pressure Steam Heating-, W^m. Kent, Vol. XIII, p. 54. Heat- 
ing- and Ventilating- a Group of Public Schools, S. R. Lewis, 
Vol. XIII, p. 187. The Combined Pressure and Vacuum Sys- 
tems of Steam Heating", G. Hoffman, Vol. XIII, p. 223. Sizes 
of Return Pipes in Steam Heating- Apparatus, J. A. Donnelly, 
Vol. XII, p. 109. Proportioning- Hot Water Radiation in 
Combination Systems of Hot Water and Hot Air Heating, 
R. C Carpenter, Vol. VII, p. 132. Tests of Radiators with 
Superheated Steam, R. C. Carpenter, Vol. VII, p. 206. Rela- 
tive Economy of Steam, Vapor, Vacuum and Hot Water 
Heating- for Residences, Vol. XII, p. 341. The Relation be- 
tween the Completeness of Air Removal and the Efficiency 
of Steam Radiators, Vol. XII, p. 315. Measurements of Wall 
Radiators, Vol. XII, p. 3 61. Advantag-es of Standard Dimen- 
sions of Radiator Valves and Connections, Vol. XIII, p. 145. 
The Relative Healthfulness of Direct and Indirect Heat- 
ing- Systems, Vol. XIII, p. 136. Improving the Heating- 
Capacity of a Radiator by an Electric Fan, Vol. VIII, p. 222. 
Engineering Record. Mechanical Plant of the Harvard 
Medical School, No. 2, Aug-. 7, 1909. Mechanical Equipment 
of the Hotel LaSalle, Chicag-o, Sept. 11, 1909. Mechanical 
Plant of the Washing-ton Municipal Bldg-., Oct. 30, 1909. 
Heating- and Ventilation of the Museum of Fine Arts, Bos- 
ton, Nov. 13, 1909. Heating- Plant for a Railway Storehouse, 
Dec. 18, 1909. Heating- and Ventilation of the Hotel Plaza, 
N. T., Mar. 13 and Mar. 20, 1909. Central Heating and 
Lighting- Plant for the United States Military Academy, May 
1, May 8 and May 15, 1900. Electric Railway Journal. Heating 
System in Car House of Toronto & York Radial Rail- 
way, March 26, 1910, p. 543. The Elevated Shops and Ter- 
minals of the Brooklyn Rapid Transit Co. — Organization and 
General Layout 'at East New York, Feb. 2, 1907, p. 170. The 
Elevated Shops and Terminals of the Brooklyn Rapid Tran- 
sit Co. — The Thirty-sixth St. Inspection Plant, March 9, 1907, 
p. 406. The Metal Worker. Unstable Water Lines in Steam 
Boilers, March 26. 1910. p. 429. Air Venting Hot Water Sys- 
tems, June 4, 1910, p. 755. Heating Swimming Pool, June 25, 
1910, p. 854. Air Venting Steam Systems, July 9, 1910, p. SO 
Heating and Ventilating Six Room School Building, Oct. 23 
1909, p. 45. Steam Heating in a Cottage, July 11, 1908, p. 
45. Indirect Hot Water Heating in Residence, Oct. 24, 1908, 
p. 43. Hot Water Heating in a Factory in Hoboken, N. J., 
April 4, 1908, p. 39. Poicer. Economics of Hot Water Heating, 
Ira N. Evans, Sept. 12, 1911. Hot Water Heating for Institu- 
tions, Ira N. Evans, May 14, 1912. Forced Circulation in Hot 
Wiiter Heating, Charles L, Hubbard, Dec. 20, 1912; Nov. 15, 



CHAPTER IX. 



3IECHANICAL. VACUUM, STEA3I HEATING SYSTEMS. 



92. In Addition to the Brief Discussion of vacuum steam 
heating- as found in Art. 69, it will be well to discuss 
more in detail the various systems by which this heating- is 
accomplished. The advantages to be derived by the positive 
withdrawal of the air and the condensation from the radi- 
ators and pipes, compared to the natural circulation of the 
g-ravity system, are now too well established to need much 
discussion. Mains and returns that are too small, horizontal 
runs of piping- that are unevenly laid so as to form air and 
water pockets, radiators that are only partially heated be- 
cause of the entrapped air, leaking" air and radiator valves, 
radiators partially filled with condensation and all the accom- 
panying- cracking- and pounding throughout many of 
the gravity systems, are sufficient causes to de- 
mand a cure, if such cure can be found. One should not 
understand by this statement that every mechanical vacuum 
system is a cure for all the ills in the heating- work, for even 
these systems may be improperly designed. The steam pipes 
may be too small to supply the radiators, although smaller 
pipes may be used in this than in the gravity work, the 
valves may be defective, or the vacuum specialties may be 
inefficient. Most of the defects in the average plant, however, 
are because of imperfections in that part of the system 
from the radiator to the boiler, and all of the first class 
vacuum systems are planned to meet just these conditions. 

Vacuum systems have other advantages over the gravity 
work, the principal one being- that of lifting the return con- 
densation to a higher level. This is noticeable in the plac- 
ing of radiators or coils in basement rooms. Another very 
important advantage is in the laying out of the heating Qoils 
for shop buildings and manufacturing plants. Low pres- 
sure gravity coils are limited to a length of about 75 feet- 
Usually the condensation .in a long coil of this kind is very 
great and requires extra heavy pressure on the steam end 
to circulate it. The steam follows the line of least resistance 



142 



HEATING AND VENTILATION 



and forces the air out of certain pipes and permits it to re- 
main in others, the differential pressure not being" great 
enough to eliminate all the air and heat the pipes uniformly. 
As a result of these conditions some of the pipes remain 
cold and ineffective as prime radiating surface. A vacuum 
system, with its poisitive circulation, increases the differ- 
ential pressure, removes the air and g-ives uniform heating 
effect in coils that are several times as long as can be 
safely supplied by the gravity system. The accumulation of 
air in the radiators and coils is especially noticeable in 
systems using exhaust steam. 

When exhaust steam from engines or turbines is used 
in a gravity heating system, the back pressure is carried 
from atmospheric pressui*e to 10 pounds gage. With the ap- 
plication of the vacuum system it is possible to maintain 
this constantly at about atmospheric pressure. It is 
claimed by some, that it is possible to reduce the pressure 
in the radiators to such a degree that the pressure in the 
supply mains will fall considerably below atmosphere. No 
doubt the specialty valves may be set so as to do this, but 
it would scarcely be considered an economical arrangement. 



y^CUUM VALVES, 

r<sH 1 1 1 1 1 1 1 h»f 
i 



:uT OFF \Aiyes> 



■HEATING M/IN 



BACK PRESSURE 
VALVE 



-lOETURN.MAjri. 



VACIUM PUMP 
BOILER FEED PUMP 



BOILER — ^ 



STEAM SEP 




mo WATER 
HEATER 



Q--® ENGINE 



|C0NDEffiER| 
JQN. PUMPlZ3=1^ 






Pig. 73. 



MECHANICAL VACUUM HEATING 143 

The principal features of a mechanical vacuum system 
are shown in Pig*. 73. Live steam is conducted to the engine 
and to the heating" main, the latter through a pressure re- 
ducing- valve to be used only when exhaust steam is insuf- 
ficient. The exhaust steam from the engines and pumps 
is conducted to the heating- main and to the feed water 
heater. The exhaust steam line opens to the atmosphere 
through a back pressure valve which is set at the desired 
pressure for the supply steam. An oil separator shown on 
the exhaust steam Hne removes the oil and delivers it to an 
oil trap. At the entrance to the feed water heater, the 
exhaust steam passes through a series of baffle plates which 
remove the oil and entrained water from that part of the 
steam which enters the heater. A boiler feed pump and a 
vacuum pump, with the attending- valves and governing ap- 
pliances, complete the power room equipment. The steam 
supply to the heating system is piped to radiators and coils 
in the ordinary Tvay, v^ith or without temperature control. 
A thermostatic valve, or patented motor valve, is placed at 
the return end of each radiator and coil and these returns 
are then brought together in a common return which leads 
to a vacuum pump or ejector. The return pipe and specialty 
valve for any one unit is usually i/^ inch. The combined re- 
turn increases in size as more radiation is taken on. Hori- 
zontal steam mains usually terminate in a drop leg Which is 
tapped to the return 8 to 15 inches above the bottom of the 
leg". Each rise in the system has a drop leg at the lower 
end of the rise. These points and all other points where 
condensation may collect are drained through specialty 
valves to the return. Water supply systems may be tapped 
for steam and return condensation the same as any ordi- 
nary radiator. Steam is carried in the main at about at- 
mospheric pressure, and just enough vacuum is maintained 
on the return to insure positive and noiseless circulation. 
In many cases where special lifts are required, these return 
systems are run under a negative presisure of 6 to 10 inches 
of mercury. Under such conditions water may be lifted 
froim 6 to 10 feet. Either closed or opened feed water 
heaters may be used with the layout as given. (For com- 
flparative sizes of gravity and vacuum returns see Table 38, 
Appendix.) 

Fig. 74 shows a section through the Marsh vacuum pump 
which represents a type very generally used in this work. 



144 



HEATING AND VENTILATION 




Fig. 74. 



It will be noticed that this pump has a steam operated valve. 
The automatic governing feature of this valve tends to 

equalize the cylinder 
pressure to meet the 
varying resistance in 
the main return of the 
heating" system. Such 
a pump is handling al- 
ternately solid water 
and vapors, hence 
there is great tenden- 
cy of the ordinary 
pump to race and 
pound at such times. 
In its operation the 
steam enters at A and 
passes into the space 
B through the annu- 
lar opening be- 
tween the reduced 
neck of the valve and 
the bore of the first chest wall. It is thus projected against 
the inside surface of the valve head before entering into 
the port and passing to the cylinder. On reaching the 
cylinder and driving the piston to the right, the reaction of 
the steam through port D to the opposite side of the valve 
head, tends to further open the steam port C. The valve 
then holds a position depending upon the relative strength 
of the forces which tend to move it in opposite directions, 
i. e,, admission steam which tends to close the valve, and the 
cylinder steam which tends to open the valve. This is 
the governing feature. It will be noticed that the pump 
piston is in two parts and carries steam at admission pres- 
sure upon the inside. This steam is admitted a^long the 
dotted line to the center of the cylinder head, thence through 
a sm-all tube and packing box to the hollow piston rod, 
which has a direct connection with the center of the piston. 
When the piston has moved sufR'ciently to bring the central 
sipace E in line with the duct D, steam is admitted to the 
right of the piston valve thus forcing it back, cutting off 
the steam at C, opening up the exhaust to the atmosphere 
through F and admitting steam to the other end of the 
cylinder. The action is thus reversed and continuous. Ejec- 



MECHANICAL VACUUM HEATING 



145 



tors operated by steam, water and electricity are also used 
to produce a vacuum. No comparison is made here of t'he 
various systems of producing- vacuum since each gives satis- 
faction when properly installed. In each case there is a 
loss of energ-y but this loss is amply repaid in the added 
benefits. 

Several patented systems of mechanical vacuum heating 
are now upon the market. These are in large measure an 
outgrowth of the original Williames System, patented in 
1882. Each system is well represented by the above diagram 
in all particulars concerning the steam and water 'circu- 
lation. The chief difference between them is in the thermo- 
static or motor connection at the entrance to each individual 
return. 

03. Webster System: — In this system a pump Is used to 
produce the vacuunr. A special fitting, called a water-seal 
motor, or thermostatic valve, is used on all radiators, coils and 
drainage points. Pig. 75 show.s a section of one of the motor 
valves. Other models are constructed so as to have the out- 
let in a horizontal direction, either parallel with or 90 de- 
grees to the inlet. Fig. 76 shows an application of this to a 
radiator or coil. The dirt strainer is usually placed between 
the radiator or coil and the motor valve. This strainer 





Fig. 75. 



Fii 



rwATER-.^AIf? 
REUEr VALVE 



CONNECT INTO 
TOP OF RETURN 

V6. 



collects the dirt and protects from clogging" the motor valve. 
C attaches to the return end of the radiator or coil and L 
leads to the vacuum pump. G is the central tube, the lower 
end of which is a valve. A is a hollow cylindrical copper 
float, the central tube of which fits loosely over spindle B. 



146 



HEATING AND VENTILATION 



The function of the cylinder A is to raise the tube G from 
the seat H and open the discharge to the pump. Ordinarily, 
the float is down and the central tube valve is resting- upon 
the seat and cuts off communication with the radiator, ex- 
cepting as air may be drawn from the radiator down the 
central tube around the spiral plug. The water of conden- 
sation accumulating in the radiator or coil passes into the 
chamber E, sealing the valve, and when sufficient water has 
accumulated to lift the float, it opens a passageway for a 
certain amount of the water to be withdrawn to the return. 
When this water becomes lowered sufficiently, the valve 
again seats itself and the cycle is completed. This action 
continues as long as water is present in the radiator. These 
motor valves are made of three sizes, V2 inch, % inch and 1 
inch. The first is the standard size and has a capacity of 
approximately 200 feet of radiation. 

Fig. 77 shows tliermostatic valves. It will be seen that 
the automatic feature in a is the compound rubber stalk, 
which expands and contracts under heat and cold. The 





Fig. 77. 



adjusting screw at the top permits the valve to be set for 
any conditions of temperature and pressure within the radi- 
ator. The water of condensation passes through a screen 
and comes in contact with the rubber stalk. The tempera- 
ture of the water being less than that of steam the stalk 
contracts and the water is drawn through the opening A by 
the action of the pump. As soon as the water has been re- 



Mechanical vacuum heating 



ui 



moved, steam flows around the stalk and expands until it 
closes the seat. This process is a continuous one and auto- 
matically removes the water from the radiator. The screen 
serves the purpose of the dirt strainer as mentioned above. 
Fig-. 77, 6, shows a sylphon arrangement where the movement 
of the valve is obtained by the expansion and contraction of 
the fluid inside the bellows. 

A suction strainer, which is very similar to the dirt strain- 
er only larger in capacity, is placed upon the return line 
next the pump. This fitting" usually has a cold water con- 
nection to be used at times to assist in producing a more 
perfect vacuum. The piping system for the automatic con- 
trol of the vacuum pump is shown in Fig-. 78. It will be 

seen that the vacuum in the re- 
turn operates through the gover- 
nor to regulate the steam supply 
to the pump cylinder, thus con- 
trolling the speed of the pump. 
Occasionally it is desirable to 
have certain parts of the heating" 
system under a different vacuum. 
An illustration of this would be 
where the radiators within the 
building were run under a neg- 
ative pressure of about one 
pound, and a set of heating coils 
in the basement were to be carried under a negative pressure 

of four pounds. The Web- 
ster System, type D, Fig. 
79, imeets this condition. 
The exact difference be- 
tween the suction pressure 
and the pressure in the 
radiators can be varied to 
suit any condition by the 
controller valve. A trap 
and a controller valve 
should be applied to each 
line having a different 




VACUUM PUMP' 

Fig. 7 




HIGH \ACUUM 



Fig. 79. 
pressure from that in the suction line. 

A modulation valve, for graduating the steam supply to the 
radiator, has been designed by this Company and may 
be applied to any Webster Heating System to assist in its 



148 



HEA'^ING AND VENTILATION 



regulation. This modulation valve serves to graduate the 
steam supply to the radiators so that the pressure may be 
maintained at any point to suit the required heat loss from 
the building-. 

94. VanAuken Systein:~In this system, as in the pre- 
vious one, the vacuum in the return main is produced by a 
vacuum pump wlhich is controlled by a specially designed 
governor. The automatic valves which are placed on the 
radiators, coils and other drainage points along the system, 
are called Belvac Thermofiers, and are shown in section by 
Fig. 80. This valve is automatic and removes the water of 

condensation by the controlling ac- 
tion of a float. It is connected to the 
radiator or coil at K and to the vacu- 
um return pipe at L. The water of 
condensation is drawn through the 
/^ return pipe into chamber D until it 
reaches the inverted weir E which 
gives it a water seal. It i.^ thence 
drawn upward into space D until it 
overflows into the float chamber AA, 
where it accumulates until the line 
of flotation is reached. Wlien the 
float G lifts, the valve seat at B 
opens and allows the water to es- 
cape into the vacuum return pipe. 
After the removal of the water the float again settles on seat 
B until sufficient water accumulates in the float chamber to 
again lift it, when the cycle is repeated. 

The air contained in the radiators or coils is drawn 
through the return and up through chamber D into the top 
of the float chamber. Here its direction follows arrows G G, 
being drawn through the small opening in the guide-pin at 
F, down through the hollow body of the copper float and 
valve seat B, into the vacuum return. This removal of air is 
continuous regardless of the amoimt of water present. The 
by-pass /, when open, allows all dirt, coarse sand or scale 
to pass directly into the vacuum return, thus cleaning the 
valve. By opening the by-pass / only part way, the con- 
tents of chamber A may be emptied into the vacuum return 
without interfering with the conditions in space D. The 
ends of the float are symmetrical, hence it will work either 
way. The thermofiers are made in four standard sizes of 




Fig. 80. 



MECHANICAL VACUUM HEATING 



149 



outlets, two having' V2 inch and two liaving % inch outlets. 
These valves have capacities of 125, 300, 550 and 1200 square 
feet of radiation respectively. 

Drop legs, strainers, g-overnors and other specialties 
usually provided by such companies are supplied in addition 
to the thermofiers. When a differential vacuum is to be ob- 
tained a special arrangement of the piping system is planned 
to cover this point. The piping- connections around the auto- 
matic pump governor are the same as are shown in Fig". 78. 
95. Automatic Vacuum System: — In this system the 
automatic vacuum valve, which takes the place of the motor 
valve and thermofier in the two preceding systems, is shown 
in Fig. 81. K is the entrance to the radiator and L to the 

vacuum return. Screen F 
prevents scale and dirt 
from entering- the valve. 
By-pass E is for emerg- 
ency use in draining off 
accumulated water and 
dirt, should the valve 
clog. With . such an ad- 
justment the bonnet of 
the valve may be re- 
moved for inspection 
without overflowing. Be- 
fore the steam is turned 
on in the radiator the float is tipped, as shown in the figure, 
making- a small wedge shaped opening through which the 
vacuum can pull on the radiator. When steam is admitted 
to the radiator, condensation flows into the valve, lifting- 
the float and sealing the outlet against the passage of 
steaim>. As the valve continues to fill with water the float 

is lifted, and water passes 
to the vacuum return. As 
the water is drawn off the 
float falls and reseats on 
the nipple when about V2 
inch of water remains in 
the valve, thus maintaining 
the water seal. Fig. 82 
shows the piping connec- 
tions around -the automatic 

pump governor. It will be 

Fig. 82. seen that this connection 





ISO 



HEATING AND VENTILATION 



differs from those of the Webster and VanAuken Systems, 
in that the pressure in the return main controls the flow 
of injection water into the suction strainer. 

96, Dunliam System: — The special valve used upon the 
returns from radiators, coils and drainage points in the 
Dunham System is shown in Fig. 83. The chamber between 
the two corrugated disks AA is filled with a liquid which 
vaporizes at low temperatures. The adjustment is so made 
that the tem,perature of the steam creates pressure enough 
between the disks to close the valve and cut off drainage 

to the vacuum pump. When 
water collects under the disks 
the temperature of the water 
RAD is sufficiently cooled below 
that of the steam 'to condense 
some of the liquid, reduce the 
pressure and open up the valve. 
The action is therefore auto- 




SUCTlONj 

Fig. 83. 



matic and controlled entirely by the temperature of the 
water or steam in contact with the disks. In other re- 
spects this system is very similar to those previously de- 
scribed. 

97. Paul System: — Referring to Art. 69 it will be seen 
that the Paul System is essentially a one-pipe system, with 
the vacuum principle attached to the air valve. Its use is 
not restricted to the one-pipe radiator, since it may be ap- 
plied to the two-pipe radiator as well. The advantage to 
be gained, however, when applied to the former, is much 
greater than in the latter because of the greater possibility 
of air clogging the one-pipe radiator. This one fact has 
largely determined its field of operation. This system dif- 
fers from the ones just mentioned in two essential points; 
first, the vacuum effect is applied at the air valve and the 
water of condensation is not moved by this means; second, 
the vacuum effect is produced by the aspirator principle 
using water, steam or compressed air, as against the pumps 
used by the other companies. The same principle may also 
be applied to the tank receiving the condensation. By this 
means it is possible to remove all the air in the system and 
to produce a partial vacuum if necessary. Ordinarily the 
vacuum is supposed to extend only as far as the air valve 
at the radiator. If desired, however, this valve may be ad- 



MECHANICAL VACUUM HEATING 



151 



justed so that the vacuum effect may be felt within the radi- 
ator, and in some cases may extend into the supply main. 
Many modifications of the Paul System are being- used. In its 
latest development, the layout of the system for large plants, 



I Ain VALVE 



AIR VALVE 



STEAn IMLET 



TO RECEIVER 
OR RETURM 




y/my//////////m^. 



TOArnOSPI-IERE 



ORAirt 



Fig, 84. 



is about the same as that shown in Fig. 73, where all of the 
principal pieces of apparatus that go to make up the power 
room equipment are present. Fig. 84 shows a typ-ical vacu- 
um connection between one-pipe and two-pipe radiators and 
the exhauster. This diagram shows the discharge leading 
to a tank, sewer or catch basin. If exhaust steam were 
used, the discharge would probably lead into the steam 
supply to one or more of the radiators and then into the 
atmosphere. Where electric current can be had this ex- 
hausting may be done by the use of an electric motor. A 
specially designed thermostatic air valve is supplied by the 
Company to be used on this system. 

Oilier vacuum systems, each having a full line of specialty 
appliances, might be mentioned here but the above are con- 
sidered sufficient. 



152 HEATING AND VENTILATION 

REFEREIVCES. 
References on 3Iechanical Vacuum Heating. 

Technical Books. 

Snow, Principles of Heating, Chap. XL. Carpenter, Heating d 
Ventilating Buildings, p. 285. Hubbard, Power, Heating & Ventila- 
tion, p. 5 68. 

Technical Periodicals. 

Engineering Review. Steam Heating Installation in the 
Biology and Geolog-y Building and the Vivarium Building, 
Princeton University (Webster System), Jan. 1910, p. 27. 
Steam Heating and Ventilating Plant Required for Addition 
to Hotel Astor (Paul System), March 1910, p. 27. Heating 
Four Store Buildings at Salina, Kans., (Moline System, Vacu- 
um Vapor), April 1910, p. 45. Steam Heating System for 
Henry Doherty's Mill, Paterson, N. J., May 1910, p. 37. Heat- 
ing Residences at Fairfield, Conn., (Bromell's System of 
Vapor Heating), June 1910, p. 52. Heating Residence at 
Flemington, N. J., (Vapor-Vacuum System), July 1910, p. 43. 
Heating. System Installed in the Haynes Office Building, 
Boston, (Webster Modulation System), Aug. 1910, p. 44. 
Heating the Silversmith's Building, New York, (Thermo- 
grade System), Jan. 1908, p. 8. Heating System in the New 
Factorv of Jenkins' Bros., Ltd., Montreal, Canada, (Positive 
Differential System), Dec. 1907, p. 14. The Railway Review. 
Vacuum Ventilation for Street Cars, Oct. 23, 1909, p. 948. 
The Metal Worker. A Vapor Vacuum Heating System, April 4, 
1910, p. 494. Heating Church by Vacuum System, Sept. 11, 
1909, p. 46. Rehabilitation by Vacuum Heating, Jan. 21, 1911. 
Poicer. Combined Vacuum and Gravity Return Heating Sys- 
tem, Charles A. Fuller, Aug. 11. 1911. Vacuo Hot Water 
Heating, Ira N. Evans. Mar. 12, 1912. Heat' & Vent. Magazine, 
Vacuum Heating Practice, J. M. Robb, Jan. 1912. 



CHAPTER X, 



MECHANICAL. WARM AIR HEATING AXD 
AENTILATIOX. FAX COIL SYSTE3IS. 



DESCRIPTION OF SYSTEMS AXD APPARATUS EMPLOYED. 

98. Fire-places, Stoves, Furnaces and Direct Radiation 
Systems of both steam and hot water have, individually, 
advantages and disadvantages, but, in common, all lack 
what is increasingly being considered as of more import- 
ance than heating, namely, positive ventilation. Merely to 
heat a poorly ventilated apartment only serves to increase 
the discomfort of the occupants, and modern legislative 
bodies are reflecting the opinion of the times by the passage 
of compulsory ventilation laws affecting buildings with 
numerous occupants, such as factories, barracks, school 
houses, hotels and auditoriums. To meet this demand for 
the positive ventilation of such classes of buildings, there 
has been developed what is variously known as the Jiot hlast 
heating system, plenum system, fan hlast system or mechanical warm 
air system. 

99. Elements of the 3Ieclianical Warm Air System:^ 

Known by whatever name, this system contemplates the 
use of three distinctly vital elements; first, some form of 
hot metallic surface over which the forced air may pass 
and be heated; second, a blower or fan of some description 
to propel the air; and third, a proper arrangement of ducts 
or passageways to distribute this heated air to desired 
locations. Figs. 96 and 97 show these essentials, fan, 
heating coils and ducts in their relative positions with con- 
nections as found in a typical plant of this system. Many 
attachments and improved mechanisms may be had to-day 
in connection with this system, such as air washers and 
humidifiers, automatic damper control systems, and brine 
cooling systems whereby the heating coils may be used 
as cooling coils, and, during hot weather, be made to 
maintain the temperature within the building from 10 de- 
grees to 15 degrees lower than the atmosphere. None of 
these auxiliaries, however, change in any way the necessity 



15-1 



HEATING AND VENTILATION 



for the three fundamentals named and their general ar- 
rangement as shown. 

100. A'ariations in tbe Desigjn of 3Iechanical Warm Air 
Systems: — .With regard to the position of the fan, two meth- 
ods of installing the system are common. The first and 
most used is that shown in- Fig. 85, a, where the fan is in 
the basement of the building and forces the air by pressure 
upward through the ducts and into the rooms. This causes 
the air within the entire building to be at a pressure 





■a. Plenum System. 



Exhaust System. 



Fij 



slightly higher than the atmosphere, and hence all leak- 
ages will be outward through doors and window crevices. 
A system so installed is usually called a plenum system. The 
fan may, however, be of the exhausting type, Fig. 85, b, 
and placed in the attic with which ducts from the rooms 
connect, so that the fan tends to keep the air of the build- 
ing at a slight vacuum as compared with the atmosphere, 
thus inducing ventilation. Air is then supposed to enter 
the basement inlet, pass over the coil surface, and, when 
heated, pass to the various rooms through the ducts pro- 
vided. But air from the atmosphere will just as readily 
leak in at windows or other crevices, as come in over the 



PLENUM WARM AIR HEATING 



155 



heaters, and then the system will fail in its heating" work. 
For this reason the exhaust heating system, as it is usually 
known, is seldom installed, except where aid in the prompt 
removal of malodors is desired. Combined plenum and ex- 
haust systems are to be recommended wherever the expense 
can be justified. 

101. Blowers and Fans: — Many methods of moving" air 
for ventilating and heating purposes have been devised; 
some positive at all times, others so dependent upon the ex- 
istence of certain conditions as to be a constant source of 
trouble. It is coming to be a very generally accepted fact, 
that if air is to be delivered at definite times, in definite 
quantities and in definite places, it must be forced there, and 
not merely allowed to go under conditions readily changing 
or disappearing. The recognition of this fact has led to a 
very common use of the mechanical fan or blower for im- 
pelling air, and this use has, in turn, caused the develop- 
ment of fans and blowers to a fairly high degree of 
efficiency. 




By the aid of mechanical apparatus, air may be moved 
positively in either of two ways, by the exhaust method or 
by the plenum method, each having fans developed be.st suited 
to its needs. In the exhaust method the fan is commonly 
of the disk or propeller blade type, shown in Figs. 86 and 



156 



HEATING AND VENTILATION 



87, ana moves the air by suction. It is usually installed in 
the attic or near the top of the building, although with a 
system of return ducts it may be installed in the basement. 
The plenum system uses a fan of the paddle wheel or mul- 
tiple blade type, shown in Figs. 88 and 89; the first is the 
standard form of fan wheel in common use, and the second 
is a more recent development of the same, called the "tur- 
bine" fan wheel, shown direct connected to a De Laval 
steam turbine. The wheels of the fans are also shown. 




Fig. 87. 



Tests of the latter wheel seem to show a somewhat higher 
efllciency than has heretofore been possible with the older 
forms. Both of these forms of fans are used in plenum 
work, and are placed on the forcing side of the circulating 
system just betTveen the air intake and the heater coils, 
or just following the heater coils, and hence produce a pres- 
sure within the building or .suite heated, so that leakages 
are outward and not so detrimental to the good working 
of the plant 'as in the exhaust system. 

The motive power for fans may be of four kinds, 
electric direct drive, steam engine or steam turbine direct 
drive, and belt and pulley drive, as shown in Figs. 87, 88, 89 
and 90. Which of these drives will be the most appropriate 
will depend entirely upon local conditions and the nature 



PLENUM WARM AIR HEATING 



157 



of the available power supply. The steam engine or steam 
turbine drive is perhaps the most common, since some 
steam must be present for the supply of the heating coils, 
and since, too, the exhaust of the engine or turbine may 
be used to supplement the live steam used for heating. 
See Art. 122. 







Fig. 88. 



Fig. 8;^. 



Fan housings are made in many different styles, and 
of various materials, the more readily to fit any given set of 
conditions. Materials employed may be of brick, wood, sheet 
steel or combinations of these. Steel housings are the most 
common and are made in such a variety of patterns as 
will fit any requirement of plenum duct direction. What 
are known as full housings are those in which the entire fan 
wheel is encased T\^ith steel and the entire unit is self-con- 
tained and above the floor line. TTircc-quavter housings are 
those in which only the upper three-fourths of the fan wheel 
Is encased, the completion of the air-sweep around the 



158 



HEATING AND VENTILATION 



paddles being- obtained by properly forming the brick foun- 
dation upon which the fan is installed. The larger fans 
are commonly three-quarter housed, especially if they are 
to deliver air directly into underground ducts. Fig. 88 
shows a full housing and Fig. 90 a three-quarter housing. 





Fig. 90. Fig. 91. 

The circular opening in the housing around the shaft 
of the wheel is the inlet of the fan, the air being thrown 
by centrifugal force to the periphery and at the same time 
given a circular motion, thus leaving the fan tangentially 
through the discharge opening. Fans may be obtained which 
will deliver at any angle around the circumference, and fans 
may be obtained with two or more discharge openings, usu- 
ally referred to as "multiple discharge fans," as shown in 
Fig. 91. Some fans have double side inlets, i. e., air enters 
the fan from each side at the center. These openings are 
smaller than the single side inlet. All fan casements should 
be well riveted and braced with angles and tee irons. The 
shaft should be fitted with heavy pattern, adjustable, self- 
oiling bearings, rigidly fastened to the casement and prop- 
erly braced. The thickness of the steel used in the casement 
varies according to the size of the fan, from No. 14 to No. 11 
for sizes in general use. The fan wheel should be well con- 
structed upon a heavy spider to protect against distortion 
from sudden starting and stopping. The side clearance be- 
tween the wheel and casement should be small. Fans should 
be bolted to substantial foundations of brick or concrete. 
When connecting them to metal ducts where 'any sound from 
the motion of the fan may be transmitted to /the room'S, the 
connection should be made through flexible rubber cloth. 



PLENUM WARM AIR HEATING 159 

102. Fresh Air Entrance to Building and to Rooms:— 

The air may enter throug-h the building- wall at the ground 
level or it may be taken from a stack built for the pur- 
pose, providing" a down draft with entrance for the air 
at the top. This may be done in case no washing or clean- 
ing systems are applied and in case the air is heavily 
charged with dust or dirt from the street. Usually in 
isolated plants or in small cities, the air is taken in near 
the ground level from some area-way that is fairly free 
from dust. In the larg-er cities, however, either a washing 
system is installed to cleanse the air before it is sent 
around to the rooms, or the air is taken from an elevation 
somewhat above the ground as spoken of before. The ve- 
locity of the air should be from 700 to 1000 feet per minute 
at this point and where grill work or shutters of any sort 
are put in the opening-, they are usually so planned as not 
to seriously obstruct the flow of the air. Usually a plain 
flat wire screen is placed in the opening to keep out leaves, 
and doors are swung from the inside in such a way as to be 
thrown open, leaving practically^ the full value of the open- 
ing as a net area. 

Air entrance to rooms is accomplished through registers 
or gratings which cover the ends of rectangular ducts or 
conduits called stacks, built into the brick walls and open- 
ing into the respective rooms much as shown in section by 
Fig. 22. Register sizes considered standard are given in 
Table 17, Appendix. The velocity of the air at a plenum 
register may be somewhat higher than in a simple fur- 
nace installation. In the plenum system the heat reg- 
isters are usually placed well above the heads of the occu- 
pants, near the ceiling, and the vent registers near the 
floor. Velocities allowable at registers and up stacks are 
shown in Table XIII, page 172. 

103. Plenum Heating Surfaces: — ^Heating surfaces as 
used to-day in connection wit'h plenum systems may be 
divided into two classes: coil surface, made of loops of 1 or 
1^/4 inch wrought iron pipe and cast surface, made of hollow 
rectangular castings provided with numerous staggered pro- 
jections to increase the outside surface and provide greater 
air contact. To make a heater of either kind of surface, 
successive units are placed side by side, until the requisite 
total area and depth have been obtaiined. The total number 
of square feet of cast or pipe coil surface exposed to the 



160 



HEATING AND VENTILATION 




air determines the total number of heat units given to the 
air per hour, w'hile the depth of the heater controls the final 
temperature of the air leaving* the heater. Each of these 
points must be considered in designing the heater system. 
(See Arts. 118 and 119). 

Pipe coils may be used 
under high pressures 
but cast coils should 
never be used under 
pressures exceeding 25 
pounds per square inch 
gage. All plenum heat- 
ing surfaces should be 
well vented and drained. 
Ample allowance also 
should be made for ex- 
pansion and contraction. 
Coil surface is of 
three kinds, that hav- 
ing" the pipes inserted 
vertically into a hori- 
Fig. 92. zontal cast iron header 

Which forms the base of the section, Fig. 92, that having 
the pipes horizontally between two vertical side headers, 
Fig. 93, and that having one header vertical and one 
header horizontal called the mitre coil, Fig. 94. The first 
and last forms shown are made with two, three or four 

pipes in depth. The stand- 
I ard number of pipes in any 
jP^ one section is four. Some- 
times these pipes are spaced 
in straight lines parallel 
with the wind and some- 
times are staggered. Stag- 
gered spacing no doubt 
f=' makes each pipe slightly 
more efficient but it adds 
friction to the air cur- 
rent and power to the fan. Efficiency tests of both spac- 
ings, however, show little difference in these methods. The 
horizontal sections and the mitre sections present this ad- 
vantage over the vertical pipe sections, that the steam and 
condensation are always flowing in the same direction and 




Fig. 93. 



PLENUM WARM AIR HEATING 



161 




Fig. 95. 



drainage is very simple. With 
the vertical pipe section, 
steam in one-half of the 
pipes must pass upward 
ag-ainst the direction of the 
flow of condensation or it must 
carry the condensation with It. 
That half of the header sup- 
plying" pipes which carry 
steam upward is usually 
drained for condensation by 
a small hole directly into the 
return with the result that 
steam often blows through 
the header without travers- 
ing the pipe circuits. The 
third, or mitre section, in ad- 
dition to perfect drainage, has 
perfect expansion. The ver- 
tical header serves as a 
steam supply and the horizon- 
tal header as a drain, permit- 
ting every pipe to assume any 
position necessary to account 
for a reasonable change of 
length. 

Cast iron radiating surface 
for plenum systems is shown 
in Fig. 95. It is composed, 
primarily, of sections not un- 
like the sections of an ordi- 
nary direct radiator in the 
way in which they are joined 
together at the top and bot- 
tom by nipples, thus forming 
what is termed a stack. Stacks 
are again assembled, one in 
front of another, with respect 
to the direction in which the 
air passes through them, the 
completed heater being then 
more or less cubical in pro- 
portion. The figure shows a 
heater two sections in depth 



162 HEATING AND VENTILATION 

and ten sections in width. Provided the conditions demand 
it, the heater may be built two or even three stacks in 
height, thus doubling- or tripling- the gross wind area. See 
Art. 119. 

(Cast iron heaters are usually of the Yento type and are 
made in two thicknesses, 6.75 and 9.125 inches in the direc- 
tion of the air velocity. They are also made in three 
heights, 40, 50 and 60 inches. These heaters present the fol- 
lowing amounts of heating surface: 6.75 inch sections — 
7.5, 9.5 and 11 square feet; 9.125 inch sections — 10.75, 13.5 
and 16 square feet of surface for the 40, 50 and 60 inch 
sections respectively. These sections give such a variety of 
sizes as to permit combinations to fit almost any possible 
requirement in net area, gross area and heating surface. 
It is unusual to assemble less than five or more than twenty- 
five sections to the stack. By the proper adjustment of 
number of sections to the stack, and of stacks to the heater, 
any requirement of hot blast work may be met. 

No matter what kind or type of heaters may be selected, 
certain methods of installing them have become common. 
They may be placed on either the suction or the force side 
of the fan, usually the former in drying or evaporating 
plants, but more often the latter in heating plants. Because 
of their weight, ample and firm foundations must be pro- 
vided. In most installations for heating purposes, w'here 
both tempered and heated air is supplied, the heater should 
be raised on its foundation 18 to 24 inches to allow a 
damper and passage way for tempered air. 

104. Division of Coil Surface: — ^It is considered best 
practice to install a hot blast heater in two parts, known 
as the tempering coil and the heating coil. In the calculations, 
Arts. 115-119, the total heating surface is first obtained and 
then this is split up into whatever arrangement is desired. 
The tempering coils should be placed in the air passage 
just within the intake for the building and sihould contain 
from one-fourth to one-third of the total heating surface. 
in this way the air is tempered before it reaches any other 
apparatus, thus protecting from accumulation of frost on 
fan and bearings and aiding in the process O'f lubrication. 
The main heat coil is placed just beyond the fan on its force 
side. Referring to Figs. 96 and 97 it will be seen that the 



PLENUM WARM AIR HEATING 



163 




PLAN. 



I II II II II II n II 





ELEVATION, 



Fig. 96. Fan Room Layout with Single Duct? along 
Basement Ceiling and all Mixing Dampers at Plenum 
Chamber. 



164 



HEATING AND VENTILATION 





Fig. 97. Fan Room Layout with Double Underground 
Ducts and Mixing- Dampers at Base of Room Stacks. 



PLENUM WARM AIR HEATING 165 

heating coils can be of service only at such times as the 
fan is in operation. If now these coils were split up into 
small heaters and placed at the foot of the stacks leading 
to the various rooms then air could be by-passed through 
the plenum chamber and ducts, over the various radiating 
surfaces to the rooms. In this way the heaters could be 
used as indirect gravity heaters. The radiation in such a 
case would be insufficient to keep the rooms at the same 
temperatures as if the same amount of surface were placed 
in the plenum coil next the fan. When the fan is in oper- 
tion the air is moving at a high velocity over the heating 
surface and the rate of transmission is very high. On the 
other hand, when they are placed at the foot of the stacks 
and used as indirect heaters, without the operation of the 
fan, the air velocity and the amount of heat delivered to 
the rooms are correspondingly reduced. In some cases the 
heating coils are arranged in this way and used when the 
building is not occupied. The convenience of such an in- 
stallation can readily be seen; however, the expense of in- 
stalling is greater than where they are assembled as coiis 
at the fan. Exhaust steam from the engine is commonly 
used in the tempering coil and live steam of low pressure 
in the main heating coil. This may be varied by conditions, 
however, and all surface supplied by exhaust steam if it is 
thought advisable. 

105. Singrle Duct Plenum System: — Duct systems in hot 
blast work may be either of the single duct type or the 
double duct type. In the single duct plant, every horizontal 
duct is carried independently from the base of the room to 
be heated to the small room called the plenum cliamher, which 
receives the hot blast from the heater. This chamber is 
divided into an upper and a lower part, the upper receiving 
the heated air that has been forced through the heater, 
while the lower part receives only air that has been through 
the tempering coils, or vice versa. The leader duct from 
the base of each vertical room duct is led directly opposite 
the partition between these two chambers, and a damper, 
regulated by some system of autom-atic control from the 
rooms to be heated, governs whether cool air from the lower 
chamber, or hot air from the upper chamber, or a mixture 
of both, shall be sent to the rooms. This system produces 
rather a complicated net work of dampers and ducts at the 
plenum chamber and this disadvantage has limited its use 
very much. 



166 



HEATING AND VENTILATION 



106, Double Duct Plenum System: — As its name indi- 
cates, this system runs a double leader duct from the 
plenum chamber to the base of each vertical room duct, the 
upper one of these ducts being in direct communication 
with the upper part of the plenum chamber and carries 

hot air, while the lower 
one is in communication 
with the lower part of 
the plenum chamber ahd 
carries cool air. No mix- 
ing- or throttling is done 
except at the base of the 
vertical room duct, where 
the mixing damper is lo- 
cated, it being controlled 
by hand or automatically 
directly from the room 
1^ n ^ ^^ ^ ni n ni rt above. With this scheme 
ffl H t ^ ^ Uj H n m D it is evident that the 

leader ducts for each 
room need not be run 
singly, but all the ducts 
having the same general 
direction combined in 
one large double trunk, 
from which branches are 
taken to the various 
room ducts as required. 
The difference between 
the two systems is shown by the two sketches, Figs. 96 
and 97. 

A hot blast plant may be installed as a basement or as 
a sub-basement system. If the former, the leaders will be 
suspended from the basement ceiling and usually con- 
structed of sheet metal, thus forming what is often called a 
*'false ceiling." If the latter, they will be just below the 
floor of the basement and will be constructed of brick and 
mortar, or of concrete, about four inches thick. For designs 
of conduits, ducts and dampers, see Figs. 90, 96, 97 and 
98, the last showing a simple and direct installation often 
applied to factories of several stories. Fig. 99 shows a 
complete steel housed plenum unit of fan, coils, dampers 
and duct connections. 




Fig. 98. 



PLENUM WARM AIR HEATING 



167 




Fig". 99. 



107. Air Washing- and Humidifying Systems: — In con- 
nection with mechanical warm air heating- and ventilating 
systems, there is often installed apparatus for washing 
and humidifying the air. In crowded city districts where 
the air is laden with dust, soot, the products of combus- 
tion and other harmful gases, its purification and moisten- 
ing becomes a most important problem. The plenum system 
of heating and ventilating lends itself most readily to 
the solution of this problem, with the result that modern 
practice is tending more each day toward the combined 
installation of ventilating and humidifying apparatus. Fig. 
100 shows a plenum system augmented by an air washing, 
purifying and humidifying apparatus. 

A purifier contemplates the installation of two parts, a 
washer and an eliminator. The washer is built in the main 
air duct, located immediately behind the tempering" coils, 
and provided with streams or sprays of water through 
-vs-hich the air must pass. Numerous schemes for breaking 
up the water in the finest sprays are on the market, and 
their relative merits may be judged from trade literature. 
Having caught the dust particles and dissolved the soluble 
gases from the air, the water falls to a collecting pan at 
the bottom of the spray chamber, and from there is again 
pumped through the spraying nozzles. As the water be- 
comes too dirty or too warm, a fresh supply is delivered to 
the collecting pan. A small independent centrifugal pump 
is commonly used for the circulation of the spray water. 

After passing through the washer, the air next encoun- 
ters the eliminator, the purpose of which is to remove the 
surplus moisture and water particles remaining suspended 
in the air. This is accomplished by an arrangement of 



168 



HEATING AND VENTILATION 



more or less complicated baffle plates, which cause the air 
to chang-e its direction suddenly many times in succession, 
with the effect that the water particles imping-e upon and 
adhere to, the baffle plates. These are suitably drained to 
the collecting- pan beneath the washer. As the air leaves 
the eliminator and enters the fan it may, with good ap- 
paratus, be relieved of 98 per cent, of all dust and dirt, may 




Fig. 100. 



be supplied with moisture to very near the saturation point, 
and, in summer time under favorable conditions, may be 
cooled from 5 to 10 degrees lower than the atmosphere. 
This is due to the cooling' effect of vaporizing" part of the 
water. 

Special air cooling" plants have been installed in connec- 
tion with the plenum system of ventilation, whereby refrig- 
erated brine could be circulated in the regular heating coils. 
The description of such a plant with data, may be found in 
the transactions of the A. S. H. & V. E. for the year 1908. 



CHAPTER XI. 



MECHAXICAIi WARM AIR HEATIIVG AlVD 
VENTILATION. FAN COIL. SYSTEMS. 



AIR, HEATING SURFACE AND STEAM REQUIREMENT. 
PRINCIPLES OF THE DESIGN. 

108. Definitions of Terms: — In the work under this gen- 
eral heading-, some of the technical abbreviations that are 
frequently used are the following": fl" = B. t. u. heat loss 
per hour by the formula, Ev = B. t. u. heat loss per hour by 
ventilation, H' = total B. t. u. loss including ventilation 
loss, Q •=^ cubic feet of air used per hour as a heat carrier, 
Q' rr cubic feet of air used including extra air for ventila- 
tion, R = total square feet of heating surface in indirect 
heaters, ts = temperature of the steam or water in the 
heaters, t = highest temperature of the air at the register 
(let this be the same as the temperature of the air upon 
leaving the heater), f =^ temperature of the air in the room, 
tv = temperature of the air at the register when extra air 
is used for ventilation, to = temperature of the outside air, 
K := rate of transmission of heat per square foot of surface 
per degree difference per hour, N = the number of persons 
to be provided with ventilation, Y = velocity in feet per 
minute and v = velocity in feet per second. Other abbre- 
viations are explained in the text. 

109. Theoretical Considerations: — For illustrative pur- 
poses, references will frequently be made throughout this 
discussion to a sample plenum design. Figs. 104, 105 and 106. 
These show the essential points of most plenum work and 
will serve as a basis for the applications. In working up 
any complete design the following points should be theo- 
retically considered for each room: the heat loss, the cubic 
feet of air per hour needed as a heat carrier (this should 
be checked for ventilation), the net area of the register 
in square inches, the catalog size of the register, and the 
area and size of the ducts. In addition to these the follow- 
ing should be investigated for the entire plant: the size 
of the main leader at the plenum chamber, the size of the 



170 HEATING AND VENTILATION 

principal leader branches, the square feet of heating sur- 
face in the coils, the lineal feet of coils, the arrangements 
of the coils in groups and sections, the horse-power and 
the revolutions per minute of the fan including- the sizes 
of the inlet and the outlet of the fan, the horse-power of 
the engine in(?luding the diameter and the length of stroke, 
and the pounds of steam condensed per hour in the coils. 

Fresh air is taken into the building at the assumed 
lowest temperature, to degrees, is carried over heated coils 
and raised to t degrees, is propelled by fans through ducts 
to the rooms and then exhausted through vent ducts to the 
outside air, thus completing the cycle. It will be the object 
to so discuss this cycle that it will be general and so it will 
apply to any case which may be brought up. 

110, Heat Loss and Cubic Feet of Air Exhausted per 
Hour: — It is assumed here, that in all mechanical draft 
heating and ventilating systems, the circulating air is all taken 
from the outside and thrown away after being used. Some installa- 
tions have arrangements for returning the room air to the 
coils for reheating, but such schemes should be considered 
as features added to the regular design rather than as being 
a necessary part of it. It is best to design the plant with 
the understanding that all the air is to be thrown away, 
it will then be large enough for any service that it is ex- 
pected to handle. Having found II by some acceptable 
formula, the total heat loss is (compare with Arts. 29 and 
36.) 

(Q or 00 (t^ — to) 
H' = H -{- (37) 

55 
When f = 70 and to = zero, this formula reduces to 
H' = H + 1.27 (0 or Q') 

To determine whether Q or Q' will be used find how many 
people would be provided with ventilating air with the 
volume Q. If Q = 5o H -~ (t — f), t — 140 and f = 70, then 

bb H H H 

N = = = approximately (38) 

1800 (t — r) 2290 2300 

If more people than N will be using the room at any one 
time, then Q' will be used instead and this value would be 
1800 times the number of persons in the room. In any or- 
dinary case, Q will be suflJicient. When this is so, formula 
37 reduces to 

H' — 2 H (39) 



PLENUM WARM AlH HEATING 171 

The reasoning" of this formula is easily seen when it is re- 
membered thcit the heat given off from the air in dropping" 
from the register temperature, 140% to the room tempera- 
ture, 70°, g-oes to the radiation and leakage losses, H, while 
that g-iven off from the inside temperature, 70°, to that of 
the outside temperature, 0°, is charged up to ventilation 
losses, Ev. Since these values are equal, W ^=^ H -\- Hv ■=■ 2 H, 
Application. — Referring" to Pig". 105, room 15, and Table 
XVI, pag"e 176, it is seen 'that the calculated he-a^t loss H, for 
this room, with f = 70 and to = 0, is 70224 B. t. u. per hour; 
also, that the cubic feet of air, Q, if * =: 140, is 54775 per 
hour. Applying formula 39, the total heat loss, H\ be- 
comes 140448 B. t. u. per hour, or twice the amount found 
by the heat loss formula. With 54775 cu»bic feet of air sent 
to the room per hour, this will provide good ventilation for 
thirty persons. Suppose, however, that fifty persons were 
to be provided for; this would require 50 X 1800 = 90000 
cubic feet of air per hour. With this increased number of 
people in the room, the total heat loss would not be as 
stated above, but would %q according to formula 37, 

90000 (70 — 0) 

E' = 70224 H = 184864. 

55 

111. Temperature of the Entering Air at tlie Register: 

— In plenum work;, the registers are placed higher in the 
wall and the velocity of the air is carried a little higher 
than in furnace work. It may be said that 140° is probably 
the accepted temperature for design, excepting where an 
extra amount of air is demanded for ventilation purposes. 
In the latter case, the temperature of the air would neces- 
sarily drop below 140° in order that the room would not be 
overheated. The general formula is 

55 E 

tv = r + (40) 

Application. — Referring to room 15 and (compare with 
Art. 38) assuming the heat loss to have been figured as 
before with ventilating air supplied sufficient for 50 per- 
sons, 90000 cubic feet per hour, then the temperature of the 
air at the register is 

55 E 

t = 10 -\ = 113° 

90000 



172 



HEATING AND VENTILATION 



The temperature of the air at the register is the 
same or slightly less than the temperature of the air upon 
leaving the coils. If this room were to be the only one 
heated, then the coils would be figured for a final temper- 
ature of the air at 113°, but other rooms may have air 
entering at higher temperatures, hence the temperature t 
upon leaving the coils should be that of the highest t at 
the registers. 

112. Cubic Feet of Air Needed per Hour: — The following 
amount of air will be needed per hour as a heat carrier 
(compare with Art. 36). 



Q = 



55 J? H 

where t = 140 and f = 70, Q = 



t — r 1.27 

If extra air be needed for ventilation, 0' = 1800 N. 



113. Air Velocities, Y, in the Plenum System: — Table 
XIII gives the velocities in feet per minute that have been 
found to give good satisfaction in connection with blower 
systems. 

TABLE XIII. 

Air Velocities in the Plenum System. 



Offices, 
schools, etc. 



Auditoriums, 
churches, etc. 



Shops and 
factories. 



Fresh 

air 
intake 



^ 



^<1 



Over 
coils 



^2 

P-l • 

. ^ 

fe O 

O r-i 

^ ?. 

O 03 

■*^ u 

<-> ® 

o > 



Main 
duct 
near 
fan 



1200 to 

1800 
say 1500 



1500 to 

2000 
say 1800 



1500 to 

3000 
say 2000 



Smaller 

branch 

ducts 



800 to 

1200 

say 900 



1000 to 

1500 
say 1200 



1000 to 

2000 
say 1500 



Stacks 



500 to 

700 
say 600 



600 to 

800 
say 700 



600 to 

1000 

say 800 



Reg'rs 
or other 
open'gs 



300 to 

400 
say 300 



400 to 

600 
say 400 



400 to 

800 
say 500 



114. Cross Sectional Area of Registers, Ducts, etc.;— 

With the above velocities in feet per minute, the square 
inches of net opening at any part of the circulating sys- 
tem can be obtained by direct substitution in the general 
formula 



A = (Q or QO X 



144 

60 y 



2.4 



(Q or Q') 



(41) 



PLENUM WARL± AIR HEATING 173 

The calculated duct sizes, of course, refer to the warm 
air duct. The cold air duct in double duct systems need not 
be so large because on warm days, when only tempered air 
is needed, the steam may be turned off from one or more 
of the heaters and the warm air duct can then be used to 
furnish what otherwise would be required from the cold 
air duct On account of this flexibility, it seems only nec- 
essary to make the cold air duct about one-half the cross 
sectional area of the warm air duct. For convenience of 
installation, therefore, it would be well to make the former 
of equal width to the latter and one-half as deep, unless by 
so doing" the cold air duct becomes too shallow. 

Applicatiox. — Assuming 2000000 cubic feet -of air to pass 
through the main heat duct, Fig. 104, per hour at the veloc- 
ity of 1800 feet per minute, the duct will be approximately 
20 square feet in cross section, or 2^/^ by 8 feet. The two 
main branches at B will carry about 800000 cubic feet per 
hour each at the same velocity and will be 7 . 4 square feet 
in area or, say 2 by 4 feet. The same branches at C will 
carry about 400000 cubic feet per hour each at a velocity of 
1500 feet per minute and will be 4.4 square feet in area or, 
say 2 by 2V2 feet and the branch D will carry about 300000 
cubic feet at a velocity of 1200 feet per minute and will be, 
say IV2 by 2% feet. 

The stack sizes were first figured for the velocity of 600 
feet per minute. These sizes were then m_ade to fit the lay- 
ing of the brick work such that the velocities would be 
anywhere between 300 to 600 feet per minute. The net 
register was figured for an air velocity of 300 feet per 
minute and the gross registers were assumed to be 1.6 
times the net area. See Art. 134. 

115. Square Feet of Heating Surface, R, in the Coils: — 

To determine theoretically the number of square feet of 
heating surface in the coils of an indirect heater, the fol- 
lowing formula may be used: 

R = (42) 

t+ to 



( "-^-) 



Rule. — To find the square feet of coil surface in an indirect 
heater, divide the total heat loss from the huilding in B. t. u. per 
hour by the rate of ti^ansmission, multiplied by the difference in 
temperature between the inside and outside of the coils. 



174 HEATING AND VENTILATION 

Since the coils are figured from the entire building' loss, 
H' will include the sum of all the heat losses of the various 
rooms. The chief concern in the use of this formula, as 
stated, is to determine the best value for Ky the rate of 
transmission. Prof. Carpenter in H. and V. B., Art. 52, 
quotes extensively from experiments with coils in blower 
systems of heating and summarizes all in the formula, K = 
2 + 1.3 V^ where v =■ average velocity of air over the coils 
in feet per second. With the four velocities most appli- 
cable to this part of the work, i. e., 800, 1000, 1200 and 1500 
feet per minute, this becomes 

800 feet per minute K = 6.9 

1000 feet per minute K — 7.3 

1200 feet per minute ^ = 7.8 

1500 feet per minute JS: = 8.5 

In the table of probable efficiencies of indirect radiators in 
Art. 54 by the same author, the values are somewhat higher, 
being 

750 feet per minute ^ = 7.1 

1050 feet per minute K = 8.35 

1200 feet per minute K ■= 9. 

1500 feet per minute K = 10. 

The values of K, as given here, are certainly very safe 
when compared to quotations from other experimenters, 
some of them exceeding these values by 50 per cent. It 
is always well to remember that a coil that has been in 
service for some time is less eflficient than a new coil, be- 
cause of the dirt and oil deposits upon the surface, hence 
it is best in .designing, not to take extreme values for ef- 
ficiency. Assuming K = 8.5 and 1000 feet per minute air 
velocity, which are probably the best values to use in the 
calculations, also ts = 227 (5 pounds gage pressure), * = 
140 and to — 0, formula 42 becomes 

R — — say (43) 

/ 140 + 0\ 1335 1400 

8.5(227 — —) 

Table XIV quoted by Mr. C. L. Hubbard in Power Heat- 
ing & Ventilation, Part III, page 557, gives the efficiencies 
of forced-blast pipe heaters and the temperatures of air 
"delivered. 



PLENUM WARM AIR HEATING 



175 



TABLE XIV. 

Efficiencies of Forced-Blast Pipe Heaters, and Temperatures 

of Air Delivered. 
Velocity of air over coils at 800 feet per minute. 



Rows 


Temp, 
will be 


to which the air 
raised from zero 


» 

Efficiency of the heating: sur- 
face in B.t.u.per sq.ft.perhr. 


of pipe 
deep 


Steam pressure in heater 


Steam pressure in heater 




5 1b. 


20 lb. 


60 lb. 


5 lb. 


20 lb. 


60 lb. 


4 


30 


35 


45 


1600 


1800 


2000 


6 


50 


55 


65 


1600 


1800 


2000 


8 


65 


70 


85 


1500 


1650 


1850 


10 


80. 


90 


105 


1500 


1650 


1850 


12 


95 


105 


125 


1500 


1650 


1850 


14 


105 


1-20 


140 


1400 


15C0 


1700 


16 


120 


130 


150 


1400 


1500 


1700 


18 


130 


140 


160 


1300 


1400 


1600 


20 


140 


150 


170 


1300 


1400 


1600 



For a velocity of 1000 feet per minute multiply the 
temperatures given in the table by . 9 and the efficiencies 
by 1.1. 

Mr. F. R. Still of the American Blower Co., Detroit, 
g-ives the following- formula for the total B. t. u. trans- 
mitted per square foot of surface per hour between the 
temperature of the steam and that of the entering- air. 



Total B. t. u. transmitted = c Vv (ts — U) 



(44) 



in which case v is the velocity in feet per second and c is 
a constant as follows: 



176 



HEATING AND VENTILATION 



TABLE XV. 

Values of c. 







Safe factor 


Max. factor 


* 

1 section 4 rows 


of pipe 


3.45 


4.40 


2 sections 8 rows 


of pipe 


3.00 


3.40 


3 sections 12 rows 


of pipe 


2.63 


2. 85 


4 sections 16 rows 


of pipe 




2.45 


5 sections 20 rows 


of pipe 


2.12 


2 20 


6 sections 24 rows 


of pipe 


1.95 


• 2.05 


7 sections 28 rows 


of pipe 


1.80 


1.95 


8 sections 32 rows 


of pipe 


1.65 


1.85 


9 sections 36 rows 


of pipe 


1.52 


1.80 


10 sections 40 rows 


of pipe 


1.40 


1.75 



From the above values of c, Table XVI has been com- 
piled, assuming ts = 227, fo = and c = a safe value. 



TABLE XVI. 



Jh —' 


Total transmissio] 


Q in B. 


t. u. per sq. 


ft. per 


hour. 


"^1 






ts — 221 


■; to — 0. 






c -^ 


































Rows of pipe deep. 






CO? 






























>B 


4 


8 


12 


16 


20 


24 


28 


32 


800 


2840 


2470 


2164 


1920 


1750 


1606 


1450 


1360 


1000 


3200 


2790 


2440 


2170 


1900 


1810 


1670 


1535 


1200 


3500 


3040 


2670 


2360 


2150 


1980 


1825 


1678 


1500 


3950 


3400 


2981 


2645 


2400 


2220 


2020 


1870 



Cast iron heaters are being used for indirect heating in 
many cases, replacing the old-fashioned pipe coil heaters. 
The efficiency of these heaters is, according to tests, about 
the same as that of the pipe coil heaters and hence formulas 
42 and 43 will apply to both pipe and cast heaters. Table 



PLENUM^ WARM AIR HEATING 



177 



XVII gives values of heat transmission for various sections, 
taken from tests upon Vento cast iron heaters set up in 
banks, and is added as a means of comparison with the 
values quoted on the pipe coil heaters. 

TABLE XVII. 

Rate of Transmission of Heat, K, through Vento Coils. 

Steam 227°, Air Entering at 0°. 



Velocities of air over coils. 



Sections 


800 


1000 


1 . 


7.6 


8.8 


2 


7.1 


8.2 


3 


6.6 


7.7 


4 


6.1 


7.1 


5 


5.6 


6.5 


6 


5.2 


6.0 


7 


4.8 


5.5 



1200 


1500 


10.0 


11.3 


9.2 


10.5 


8 6 


9.7 


7.9 


90 


7.3 


8.3 


6 7 


7.7 


6.2 


7.1 



In applying these values of K to formula 42 it should 

be remembered that to would be used instead of - — t-—^ — 
Application^ 1. TT/zere Heating Only is Considered. — Referring 
to Table XXV let E for the entire building be 1483251. 
Then from Art. 112, Q = 1156935, by formula 39, H' — 2966502 
and by formula 43, the coil surface is 



2966502 



R = 



8.5 



= 2222 square feet. 



/ 140 + \ 

0" — r-) 



With three lineal feet of 1 inch pipe per square foot of 
surface, we have 6666 lineal feet of coils in the heater. 

Application 2. Where Ventilation is Considered. — Assume 1100 
people in the building on a zero day and Q' = 2000000, then, 
H' = 148.3251 + 1.27 X 2000000 = 4023251 and 

4023251 

= 3014 sq, feet = 9042 lineal feet. 



R = 



H 



227 



140 + 



) 



178 HEATING AND VENTILATION 

This value is probably the greatest amount that would 
be needed. In such a case, when the rooms are supplied 
with extra air, the register temperatures over the entire 
building may be less than 140 degrees. Suppose in this 
case the temperature is, by formula 40, * = 70 + 55 X 1483251 
-T- 2000000 = 111°, then 

4023251 

R — = 2760 sq. ft. = 8280 lineal ft. 

/ 111 + \ 

In using this formula, the value t = 140 is to be recom- 
mended wherever part of the rooms are not provided with 
extra amounts of ventilating air. By so doing the ducts and 
registers may be held down to a more moderate size and at 
the same time give a safer figure for the heating surface. 

Suppose that in a certain building most of the rooms 
are to be ventilated and that these rooms will have large 
amounts of air delivered at low temperatures. In such a 
case it will be economy to heat the air for all rooms to this 
temperature and supply more air to the rooms that would 
otherwise be heated with air at 140 degrees, than to put 
in a heater large enough to heat all the air to 140 degrees 
and then dilute with large amounts of cold air to lower the 
temperature to what it should be. Again, suppose that a 
school building contains, in addition to the regular class 
rooms, laboratories, etc., an auditorium and gymnasium, the 
two together requiring an amount of air sufficient to justify 
a separate fan system (a condition which frequently exists), 
it would be economy to separate the heating system for 
these rooms from the rest of the building because of the 
comparatively short time the rooms are in use. When not 
in use the fan unit may be shut down without interfering 
with the rest of the system. On the other hand, if united 
with the rest of the building, the cap-aoity of the unit would 
be reached only when these rooms were in use, while at 
otiher times it would run at a very low efficiency. 

116. Approximate Rules for Plemini Heating; Surfaees: 

— The following approximate rules are sometimes used in 

checking up heating surface in the coils. These are not 

recommended and should be used with caution. 

Rule 1. — ''Allow one lineal foot of 1 inch pipe for each 65 to 
125 cuhic feet of room space''; 65 for office huildings, schools, etc., 
and 125 for shops and laboratories. Since this huilding has approx- 
imatcUi 500000 cubic feet of room space, it gives 7700 lineal feet 
of 1 inch pipe in the heater. 



PLENUM WARM AIH HEATIN(^ 



179 



Rule 2. — ^^Alloiv 200 lineal feet of 1 inch pipe for each 1000 
cubic feet of air per minute at a velocity of 1500 feet per 7ninute/' 
Applying to the above building when the air moves over the coils at 
1000 feet per minute, the heated surface is only about four-fifths as 
valuable and would require 250 lineal feet per each 1000 cubic feet 
of air per minute. This gives 8333 lineal feet of coils. 

117. Final Air Temperatures: — Since the amount of 
heat transmitted is directly proportional to the difference 
of temperature between the two sides of the metal, the first 
coils in the bank are the most efficient, and this efficiency 
drops off rapidly as the air becomes heated in passing- over 
the coils. Final temperatures for different numbers of coil 
sections in banks have been found by experiment and may 
be taken from Table XVIII. See also Table XIV, page 175. 



TABLE XVIII. 

Temperatures of Air upon Leaving Coils, Steam 227°, Air 

Entering at 0°. 







Velocities of air through coils in F. P. M. 


Sections 


No. of 
Rows 






890 


1000 


1200 


1500 


1 


4 


42- 


33 


28 


23 


2 


8 


71 


62 


56 


52 


3 


12 


96 


87 


80 


75 


4 


16 


119 


108 


101 


93 


5 


£0 


136 


125 


116 


108 


6 


24 


153 


140 


131 


120 


7 


28 


169 


155 


143 


131 


8 


32 


183 


166 


154 


141 



These temperatures may be increased about 10 per cent, 
for 20 pounds gage pressure. 

Table XIX shows similar results quoted for the Vento 
cast iron heaters. 



180 



HEATING AND VENTILATION 



TABLE XIX. 

Temperatures of Air upon Leaving Vento Coils, Steam 227°, 

Air Entering at 0°. Regular and Narrow Sections 

5 Inch Centers. 



Pi 
























Velocities of air through coils in F. P. M. 






800 


1000 


1200 


1500 






0° 


-10° 


-20° 


0° 


-10° 


-20° 


0° 


-10° 


-20° 


0° 


-10° 


-20° 


1 


Heg. 
Nar. 


88 






85 






82 






30 






2 


Reg. 


C8 


61 


65 


68 


55 


48 


59 


51 


44 


53 


45 


38 




Nar. 


51 


48 


36 


46 


88 


31 


48 


85 




89 


31 




3 


Reg. 


98 


87 


82 


87 


80 


75 


82 


75 


69 


74 


68 


61 




Nar 


70 


64 


57 


65 


58 


52 


61 


54 


47 


55 


48 


41 


4 


Reg. 


113 


108 


103 


106 


100 


96 


100 


95 


90 


92 


86 


81 




Nar. 


88 


82 


77 


82 


76 


70 


77 


70 


64 


70 


63 


56 


6 


Reg. 


130 


126 


122 


122 


118 


114 


116 


111 


107 


108 


102 


97 




Nar. 


108 


97 


93 


96 


90 


86 


90 


84 


80 


83 


77 


71 


6 


Reg. 


148 


140 


136 


186 


132 


128 


129 


125 


121 


120 


116 


112 




Nar. 


115 


111 


107 


108 


104 


100 


102 


98 


93 


94 


89 


84 


7 


Reg. 


154 


151 


148 


147 


144 


141 


141 


137 


133 


132 


128 


124 




Nar. 


127 


123 


120 


120 


115 


111 


114 


109 


105 


105 


100 


96 



118. Arrangement of Coils in Pipe Heaters: — Coil sec- 
tions are arranged with 2, 3 and 4 rows of pipes per sec- 
tion. Unless special reference is made to this point, the 
latter value is understood. Having found the total square 
feet of heating surface in the heater, obtain from the tem- 
perature tables the number of sections deep the heater will 
need to be to produce the desired temperature, and find the 
number of square feet of heating surface per section and 
per row of coils. Let this latter value be A. Also find the 
net wind area across the coils, assuming, say 1000 feet per 
minute velocity. From the net wind area, find the gross 
cross sectional area of the heater by the value 

Gross wind area = 2.5 times net wind area. (45) 

From the gross area the size of the heater may be selected. 
In selecting the heater, the following check should be ap- 
plied. Find the number of square feet of heating surface, 
B, in each row of the coils as figured from the gross area 
and compare with A. These must be made to agree. 

Let the net area between the tubes, N, A., the space 



PLENUM WARM AIR HEATING 181 

occupied by the tubes, T, A., and the gross cross sectional 
wind area through the tube, G. W. A., be respectively 

^' ^- - -Tr. ' ^- ^' ~ ' and a. W. A, = (46) 

60 y 40 F 24 F 

Since the cross sectional space T, A. occupied by the tubes 
is to the coil surface per row as 1 : 3.1416, the total coil 
surface in one row of tubes is 

3.1416 (Q or Q') (0 or Q') 

^1 = =: .08 



40 V V 

Reduced to the basis of the net area, N. A., we have 

Bi — 4.8 times 2V. A. (47) 

If 5 is g-reater than A, then the total heating surface 
must be increased in that proportion, since the number of 
sections cannot be less or the final temperature will drop 
below the required degree, and the net cross section cannot 
be less or the velocity of the air will be greater than that 
desired. On the other hand, suppose B should be less than 
A, In that case the total heating surface will not change 
from that calculated. Either B may remain the same as 
calculated and the number of sections increased (if de- 
sirable) until all the heating surface is accounted for, or A 
may remain constant and B may be increased. The latter 
method is probably a better one since it gives larger wind 
areas and consequently reduced velocities of the air, which 
in many cases is desirable, and avoids placing heating ,sur- 
face at the rear of the bank where it is less efficient. 

Assembled sections of pipe coil heaters are supplied by 
manufacturers from the smallest size of 3 feet x 3 feet, to 
the largest size of 10 feet x 10 feet; these dimensions being 
those of the gross cross-sectional area, and not dimensions 
overall. Between the two limits, both height and breadth 
usually vary by 6 inch increments. For exact sizes, consult 
dimension tables in manufacturers' catalogs. 

Application 1. — In Article 115, let R — 2222, Q = 1156935, 
V — 1000 and t = 140; then from Table XVIII the heater will 
require 24 rows of coils in depth to give the required tem- 
perature. Next find Ri = 93 square feet of heating surface 
per row, also 

I^. A. =: 19.7; T, A. = 29.6; and G. W. A. = 48.3. 
Checking N. A. with an air velocity of 1000 feet per min- 
ute gives 1156935 -f- (60 X 1000) = 19.3 square feet, which 



182 HEATING AND VENTILATION 

shows that the above arrangement is satisfactory. Now 
from the value G, W. A, = 48.3 select a heater, say 6 feet 
X 8 feet. 

Application 2.— In article 115, let R = 3014, Q' = 2000000, 
F = 1000 and t = 140; then as before, the heater will need 
24 rows of coils. Find in this case i?i = 126 and 

A'. A. = 26.3; T. A. = 39.4; and G. W. A. — 65.7. 
Checking from the volume of air delivered, obtain 

JV^. A, — 33.3; T. A. = 50; and G. W, A. = 83.3. 

From N. A. = 33.3 find Rx = 160, which shows that it will 

160 

be necessary to increase the total heating surface to 

126 

X 3014 = 3826 square feet. If it were considered advisable 
to have 1200 feet air velocity the heating surface per row 
would be reduced to 135 and the temperature, t, would be 
reduced to 131. Both conditions are reasonable and in many 
cases would be considered satisfactory. 

Selecting the heater for the gross area of 83.3 square 
feet, from the catalog size, would probably give a single 
section 9 feet X 9 feet or a double section, each part 6 
feet X 7 feet. 

119. Arrangement of Sections and Stacks in Vento Cast 
Iron Heaters: — Applying only to Case 2, Art. 115, let R = 
3014, g' = 2000000, y = lOOO, N, a. (least value) = 33.3, and t 
= 140. 

From Table 48, Appendix, either of the following ar- 
rangements will give the necessary y. A. First. — Six stacks 
deep, two sections high, 50 inches on top of 60 inches and 
twenty sections wide. This makes a total of 590 square 
feet to the stack or 3540 square feet total. The gross wind 
area looking in the direction of the wind is 103 inches by 
110 inches. Second. — Six stacks deep, two sections high, 60 
inches on top of 60 inches and eighteen sections wide. This 
makes a total oif 576 square feet to the stack or 3456 square 
feet total. The gross wind area looking in the direction 
of the winci is 93 inches by 120 inches. These arrangements 
will guarantee a temperature of 136 degrees upon leaving 
the coils. If this temperature is not sufficient then the 
coils must be made seven sections deep and the total heat- 
ing surface arbitrarily increased. Other arrangements 
could be worked out with 4% inch and 5% inch spacings. 
Also, narrow sections could be used in place of the regular. 
It will be found, however, that the two stated are probably 



PLENUM WARM AIR HEATING 183 

the best arrangements that could be made. (See Table XIX 
for temperatures.) 

120. Use of Hot Water in Indirect Coils: — In most cases 
low pressure steam is used as a heating medium in the in- 
direct coils. It is possible, however, to use hot water in- 
stead, where a good supply is to be had. In such an ar- 
rangement the coils will be figured from formula 42, using 
all values the same as for steam excepting ts, which will 
be replaced by the average temperature of the water. The 
piping connections and the arrangement of the coils will 
follow the same general suggestions as already stated. 

121. Pounds of Steam Condensed per Square Foot oi 
Heating Surface per Hour: — From Art. 115 the number of 
pounds of condensation per hour per square foot of surface 
in the coils is 

E' 

m = (48) 

R X Heat given off per pound of condensation. 

Application. — Let R = 3014 and H' = 4023251; also let 
one pound of dry steam at five pounds gage in condensing 
to water at 212 degrees give off 1155.6 — 180.9 = 974.7. (See 
Tables 4 and 8, Appendix), then 

4023251 

m = =1.37 pounds. 

3014 X 974,7 

This amount should, of course, be considered an average. 

The first and last section in any bank would vary above 
and below this amount by as much as 50 per cent, in the 
average plant. The first coils may condense as much as 2 
pounds of steam per square foot of surface per hour. 

122. Pounds of Dry Steam Xeeded in Gxcess of the 
Exhaust Steam Given off From the Engine: — Let the heat- 
ing value of the exhaust steam from the engine be 85 
per cent, of that of good dry steam, also let the engine 
use 40 pounds of dry steam per horse power hour in driv- 
ing the fan. From Art. 132, the engine will use 40 X 13.6 
= 544 pounds of steam per hour and the heating value will 
be 974.7 X .85 = 828 B. t. u. per pound or 828 X 544 = 450432 B. 
t. u. total per hour. Then 4023251 — 450432 = 3572819 B. 
t. u., and 3572819 -i- 974.7 = 3664 pounds of steam. The 
boiler will then supply to the engine and coils, 3664 + 544 
= 4208 pounds of steam total and will represent, approx- 
imately, 4208 -7- 30 = 140 boiler horse power. 



CHAPTER XII. 



MECHANICAL, WARM AIR HEATING AND 
VENTILATION. FAN COIL SYSTEMS, 



PRINCIPLES OP THE DESIGN, CONTINUED. 
FANS AND FAN DRIVES. 

123. Theoretical Air Velocity: — The theoretical velocity 
of air V, flowing" from any pressure, pa, to any pressure, pb, 



is obtained from the general equation v = y/2g1i, where v 
is given in feet per second, g = 32.16 and li = head in feet 
producing flow. This latter value may be easily changed 
from feet of head to pounds pressure and vice versa. 

When exhausting air from any enclosed space into 
another space containing air at a different density, the 
force which causes movement of the air is pa — pb =■ px. 
These recorded pressures may be taken by any standard 
type of pressure gage and show pressures above the at- 
mosphere. When exhausting into the atmosphere, the value 
pb is zero and pa = px. The fact that a difference of pres- 
sure exists between two points indicates that there are 
either two actual columns (or equivalent as in Fig. 8) of 
air at different densities connected and producing motion, 
or that, by mechanical means, a pressure difference is crea- 
ted which may easily be reduced to an equivalent head h, 
in feet, by dividing the pressure head by the density of the 
air, as 

pressure difference pa — ph 



n = 



density d 

Let Pa — Pb = Px = ounces of pressure per square inch of 
area producing velocity of the air; also, let g = acceleration 
due to gravity = 32.16 and d = density, or weight, of one 
cubic foot of dry air at 60 degrees and at atmospheric pres- 
sure (Table 12, Appendix), then, substituting an the general 
equation, we have 



^=v 



64.32 X 14ipx 

= 87 Vp» (49) 



.0764 X 16 

Since the pressure producing flow is usually measured 
in inches of water, hw, the above can be changed to equiva- 
lent height of air column by 

weight of water, per cu. ft. at given temp. X hio 
h — — _ (50) 

weight of air at given temperature X 12 



PLENUM WARM AIR HEATING 185 

Applying" this to dry air at 60 degrees and water at the 
same temperature (Tables 12 and 8, Appendix, also Art. 15), 

62.37 hic 

h = = QS Jiw 

12 X .0764 

then substituting in the general equation, find 



V = V64.32 X 68 hw = 66.2 Vhiv (51) 

Formula 50 at the temperatures 50, 55, 60, 65 and 70 
degrees respectively, gives results varying between r == 65.5 
y/ir^ tor 50 degrees and v = 66.5 VX^ for 70 degrees, which 
leads to the approximate general rule that the theoretical 
velocity of air, ichen measured ty a icater column gage that meas- 
ures in inches of icater, equals sixty-six times the square root of the 
height of the column in inches. Stated as a formula 

1? = 66 V"^ (52) 

for calculations re-quiring' accuracy, several factors af- 
fect the final result; atmospheric pre.ssure, humidity, and 
the density and change of temperature in the air current. 
Let the atmospheric pressure and the humidity be 
constant, since these would affect the result but little, and 
first take into account the density of the air. Let the 
pressure of the atmosphere be 29.92 inches of mercury 
(14.7 pounds = 235 ounces per square inch area) then, 
since the density is pr.oportional to the absolute pressure, 
the temperature remaining constant, we have from form- 
ula 49 with air exhausting into the atmosphere. 



64.32 X 144 px j px 



V 64.31! X 144 Px I 
= 1336 ^ 
235 + Px \ 235 + Px 
.0764 X 16 X 



(53) 



235 
Also from the relation existing between formulas 49 and 
51, formula 53 reduces to 



u = 1336 ^ • (54) 

\ 407 H- hw 
From formulas 53 and 54 the second columns in Tables 

XX and XXI have been calculated. 

Applicatiox. — Air is exhausted from an orifice in an air 
duct into the atmosphere. The pressure of the air within 
the duct is one ounce by pressure gage or 1.74 inches by a 
Pitot tube. Assuming the air to be dry and the barometer 
standing at 29.92 inches when the water in the tube is 60 
degrees, what is the velocity of the air? By the approxi- 
mate formulas 49 and 52 



3S6 



HEATING AND VENTILATION 



i; =: 87 VI = 87 F. P. S. 



and i; = 66 VI-'' 4 = 87.2 7^. P. 8. 
By formulas 53 and 54 



V = 1336 J = 86.3 F. P. 8, 

^ 235+1 

and V = 1336 A = 87.1 P. P. 8. 

^ 407 + 1.74 

TABLE XX. 

Column 2 figured from formula 53. 



oa 

is 


Velocity of dry air at 60o es- 
caping into the atmosphere 
through any shaped orifice in 
any pipe or reservoir in which 
a given pressure is main- 
tained. 


Vol. of air in cu. 
ft. which may be 
discharged in 1 
min. through an 
orifice having an 
effective area of 
discharge o f 1 
sq.inch. 

Ool. 3 -^ 144 


H. P. required to 
move the given 
vol. of air under 
the given con- 
ditions o f dis- 
charge. 

(Col. 3 X Col. 1) 




Ft. per sec. 


Ft. per min. 




£ 


16 X 33000 


/8 


30.80 


1848.00 


12.83 


0.CC044 


K 


43 56 


2613.60 


,18.15 


0. 00124 


Vs 


£3.27 


3196 20 


22.19 


0.C0227 


H 


61. £6 


3693.60 


25-65 


0.00349 


Vb 


68.79 


4127.40 


28 66 


0.C0489 


H 


75.35 


4^:21.00 


31.47 


0.00642 


rs 


81. C7 


4882 20 


33.90 


0.C08C9 


1 


86.97 


£218.20 


36-24 


0.CC988 


\% 


.92.18 


5C30.80 


88.41 


0.01178 


IK 


97 18 


£830.80 


40.49 


0.01380 


P/8 


101.90 


6114. CO 


42.46 


0. 01592 


IM 


106.40 


6384. CO 


44.33 


0.01814 


m 


110.82 


6649.20 


46.11 


0.02046 


VA 


114.86 


6891.60 


47.86 


0.02284 


VA 


118.85 


7ia 00 


49.52 


0.02533 


2 


122 47 


7ai8.20 


51.03 


0.02787 



PLENUM WARM AIR HEATING 



187 



TABLE XXL 

Column 2 fig-ured from formula 54. 





Velocity 


of dry air at 60o escaping into the atmosphere 


Pressure 


through 


any shaped orifice in any pipe or reservoir in 


head in 


which a 


gfiven pressure is maintained. 


inches of 






water 










Feet per second 


Feet per minute 


1 




29 04 


1256.40 


.2 




29.67 


1780 20 


.3 




36.25 


2175.60 


A 




41.86 


2511 60 


.5 




46.80 


2708. 00 


.6 




51.26 


3075.60 


.7 




55 36 


3321.60 


.8 




59.10 


8546.00 


.9 




62.60 


8756.00 


1. 




66.14 


8968.40 


1 1 




69.36 


4161.60 


1 2 




72.44 


4346.40 


1 3 




75 39 


4523.40 


1.4 




78.21 


4692.60 


1.5 




80.96 


4857.60 


1 6 




83 £9 


5015.40 


1.7 




86.16 


5169.60 


18 




88.65 


5319 00 


19 




91.27 


5476.20 


2. 




93.42 


5605.20 


2.1 




95.72 


5743.20 


2 2 




97 96 


5877.60 


2 3 




100 15 


6009.00 


2.4 




102.29 


6137.40 


2 5 




104.89 


6263.40 


2 6 




106.43 


6385.80 


2 7 




108.46 


6507 60 


2.8 




110.43 


6625.80 


2 9 




112.37 


6742.20 


3. 




114.28 


6856.80 


3 1 




116.15 


6969.00 


8 2 




118 00 


7080.00 


3 3 




119.81 


7188.60 


8 4 




121.60 


7296.00 


3.5 




123.36 


7401.60 



Finally, after considering- the change of velocity that 
takes place when the density changes v^ith a constant tem- 
perature, let the temperature change. With a constant 
pressure, the volume changes with the absolute temperature 
(460 + t). From this basis the values g-iven in the seconc 



li>8 



HEATING AND VENTILATION 



columns of Tables XX and XXI, which were figured for 60 
degrees, would be multiplied by the relative factors for 
the given temperature as expressed in column two, Table 
XXII, to obtain the velocity of the exhausting air at any 
pressure and any temperature. Having found the data 
from Column 2, find other points of information concerning 
velocities, pressures, weights and horse powers in moving 
air by multiplying by the factors as given in the respective 
columns. 

TABLE XXII. 





Factor for rel- 








s 


ative vel. at 
same pressure 
also relative 


Factor for 
relative pres- 
sure, also wt. 
of air moved 
at same ve- 
locity = 


Factor for rel- 
ative vel. to 
move same 


Factor for rel- 
ative power to 


1 

a 


powers to 
move same 
vol. of air at 
same vel. = 


wt. of air also 
relative pres- 
sure to pro- 
duce the vel. to 


move same 
wt. of air at 
vel. in column 
4 and pressure 


d 

a 

0) 




460O + 60O 
T 


move same wt. 
of air = 


in column 4 = 
factor in col- 
umn 4 squared 


/ Wt. at any T 


H 


\Wt, at 4600 + 600 




1 ^ Col. 3. 




30 


.^ 


1.07 


.93 


.87 


40 


.98 


1.04 


.96 


.92 


50 


.99 


1.02 


.98 


.96 


60 


1.00 


1.00 


1.00 


1 00 


70 


1.01 


.98 


1.02 


1.04 


80 


1.02 


.96 


1.04 


108 


90 


1.03 


.94 


1 06 


1.13 


100 


1.04 


.92 


1.09 


1.19 


125 


1.06 


.89 


1.12 


1 25 


150 


1.08 


.85 


1.18 


1.39 


175 


1.10 


.82 


1.22 


1.49 


200 


1 13 


.79 


1.27 


1.61 


250 


1.17 


.73 


1.37 


1.88 


300 


121 


.68 


1.47 


2.16 


350 


1.25 


.64 


1.56 


2.43 


400 


1.28 


.60 


1.67 


2.79 


5C0 


1.36 


.54 


1.86 


842 


600 


1.43 


.49 


2.04 


4 16 


700 


1.49 


.45 


2.22 


4. 93 


800 


1.56 


.41 


2.44 


5.95 



124. Actual Amount of Air Exhausted: — When air of any 
pressure is exhausted from one receptacle to another through 
an orifice, the actual velocity remains about the same as 
the theoretical velocity, being slightly reduced by friction, 
but the volume of air discharged is greatly reduced because 



PLENUM WARM AIR HEATING 



189 



of the contraction of the stream just as it leaves the ori- 
fice. The greatest contraction or least size of the jet is 
located from the orifice a distance of about one-half the 
diameter of the opening". A round ofpening is the most effi- 
cient. Since the velocity is slightly reduced and the effec- 
tive area of the opening reduced a still greater amount, the 
actual amount of air exhausted in any given time will be 
found by multiplying the theoretical amount by a constant 
which is the product of the coefficient of reduced velocity 
and the coefl^cient of reduced area. From tests by Weisbach 
the following approximate values are quoted by the Sturte- 
vant Company in Mechanical Draft, page 152. 

Orifice in a thin plate, .56 

■Short cylindrical pipe, .75 

Rounded off conical mouth piece, .98 

Conical pipe, angle of convergence 

about 6% .92 

1^5. Results of Tests to Determine the Relation be- 
tween Pressure and Velocity in Air Transmission: — In fan 

construction the number of blades, the shape of the blades, 
the sizes of the inlet and outlet openings, the shape and 
size of the casement around the blades and the speed, all 
have an effect upon the relation between the pressure and 
the velocity of the air discharge. From recent tests con- 
ducted in the Mechanical Engineering Department, Univer- 
sity of Nebraska, the curves shown in Fig. 101, a, were ob- 




3 4 5 

RATIO or OPENING 

Fig. 101a. 



O 



190 



HEATING AND VENTILATION 




2 .3 4 5 .6 
RATIO Of OPENING 

Fig. 101b. 



tained. A Number 2 Sirocco blower was belted to an elec- 
tric motor and delivered air to a horizontal, circular pipe 
whose length was nine times the diameter. This pipe was 
provided with -reducing nozzles which varied the area of 
discharge by 'tenths from full opening to full closed. The 
air tube was provided also with manometer tubes for static, 
dynamic and velocity pressures, arranged with an adjustable 
scale to read to either .01 or .002 inch of water. The gross 
power was taken by wattmeter and the delivered power 
from motor to fan was taken by dynamometer. In addition 
to this, the frictional horse-power of the fan and motor 
unit was obtained by removing the fan wheel from the 
shaft and taking readings with all other conditions remain- 
ing as nearly constant as possible. The friction power, 
when deducted from the gross power recorded by the watt- 
meter, gave the readings for the net horse-power curve. 
A galvanized iron intake, enlarged from the size of the 
fan intake to a rectangle four square feet in area and 
divided up by fine wires into rectangles the size of the 
standard anemometer, was used to find the volume of air 
moved per minute. This volume is shown in the curve 
C. F. M. To check the curve, the volume was calculated for 
each opening by the Pitot tubes on the side of the experi- 
mental pipe. 



PLENUM WARM AIR HEATING 191 

To fully understand this article, refer to Art. 15 and note 
that J., Fig-. 10, registers static pressure plus velocity pressure. This 
sum may be called the dynamic pressure. Also, note that B reg- 
isters only static pressure, i. e., that pressure which acts equally 
in all directions and serves no usefulness in moving the air. 
Also, note that A — B = C, i. e., dynamic pressure minus 
static pressure equals velocity pressure. When applied in 
the form shown by C, the pressure recorded is that due to 
the velocity only. This is the form commonly used. Now 
referring- again to Fig. 101, A. V. P. is that pressure re- 
corded by C when applied .to the air current at the fan out- 
let, = air velocity pressure. P. V. P. is that pressure (ob- 
tained by formulas 49 to 54) that would be shown on C if 
the air were moving as fast as the tip of the blades on the 
fan wheel, = peripheral velocity pressure. P. Y, P. = i in 
Fig-. 101, b. D. P. is the dynamic pressure and would be 
found by applying A only. 8, P, is the static pressure as 
stated above. 

In the tests, the fan was run at constant speed and the 
dynamic, static and velocity pressures were measured about 
midway of the pipe at full opening-. Then the openings were 
changed by ten per cent, reductions until the pdpe was fully 
closed and similar reading-s taken for each reduction. T-hese 
readings were plotted in the upper set of curves. Because 
of the fact that the manometer tubes were located some 
distance from the end of the experimental pipe, there was a 
static pressure, ab, recorded at full opening. This caused 
the dynamic pressure to be raised a corresponding amount, 
a' b\ If the tubes had been located at the delivery end of 
the pipe the static and dynamic pressures would have fallen 
from b and &' to a and a\ The peripheral velocity of the 
wheel was 2828 feet per minute and the corresponding pres- 
sure, with corrections for temperature, was found by formula 
52 to be .5 in. of water. The relation between this peripheral 
velocity pressure and the air velocity pressure is shown in 
the lower set of curves. In applying the lower curves to 
fan practice they are very valuable in showing the relation 
between the velocity of the wheel circumference and that of 
the air leaving the wheel. Notice that the relation between 
the observed air velocity pressure and the calculated periph- 
eral velocity pressure at full opening and discharging into 
free air, is 1.20 : 1. Since the velocities vary as the square 
roots of the pressures (v = V'mJ, we find the velocities to 



192 HEATING AND VENTILATION 



be VI. 20 : VI = 1.1 : 1. That is to say, for this fan the air 
velocity at the free opening- of the fan is 1.1 times the per- 
ipheral velocity of the wheel. The corresponding" velocity 
of the air from the average steel plate fan as reported by 
the American Blower Company and as shown on the lower 
chart, is V.45 : Vir~= .67 : 1, or .61 of the speed of the 
Sirocco fan for the same wheel speed. The resistance offered 
by the ducts in the average plenum heating system is 
equivalent, we w^ill say, to that offered by a 75 per cent, 
gate opening in the experimental pipe. According- to the 
diagraims for this opening", the ratio A. Y. P. to P. Y. P is 
1.04 for the Sirocco fan and .25 for the steel plate fan. The 
ratio of the air velocities to the peripheral velocities then 
are, respectively, Vl704 : VlT^ 1.02 : 1 and V.25 : Vr~= .5 : 1. 
These show that with a 75 per cent, opening and with the 
fan wheels running with a peripheral velocity of 3000 feet 
per minute, the air would be entering the ducts at 
1.02 X 3000 = 3060, and .5 X 3000 = 1500 feet per minute 
respectively for the two types. Conversely, if it were de- 
sired to ihave the air enter the ducts at 1500 feet per minute, 
with a resistance equivalent to a 75 per cent, opening, the 
fan wheels would have peripheral speeds of 1500 -j- 1.02 = 
1470, and 1500 -r- .5 = 3000 feet per minute respectively. 
From these we obtain the wheel diameter for any given 
R. P. M. Other models of the Sirocco and multiple blade 
type of fans show less variation from the steel plate fan 
than the one under 'Consideration. It will be seen from the 
above that the late change in construction from the steel 
plate type to the multiple blade type permits a smaller 
wheel and fan to be installed for any given work. This can 
be shown to be a desirable change. From formula 61, it is 
seen that the power required to drive a fan varies as the 
fifth power of the diameter and as the cube of the speed. 
With any given amount of air, Q, required per minute, the 
power will be reduced very greatly by reducing" the diam- 
eter or by reducing the speed of the fan. Manufacturers' 
catalogs should be consulted for capacities, sizes, etc. Such 
tables are supplied by the trade in form for easy reference 
and use. 

126, Work Performed and Horse-Povrer Consumed in 
Moving Air: — The foot pounds of work performed in moving 
air equals the product of the moving force into the distance 



PLENUM WARM AIR HEATING 193 

moved through in any given time. Let Va — pb = pa; = 
moving force of the air in ounces per square inch and A = 
cross-sectional area of current in square inches. Then the 
pounds per square inch will be px -^ 16, and the foot pounds 
of work, TT, and the horse-power, H. P., absorbed per min- 
ute by the current of air in being moved, will be 

^Q Px A V 

W = = 3.75 px A V (55) 

16 

8.75 Px Av 

E. P. = = .000114 Px A V (56) 

33000 

This formula may be stated in terms of the cubic feet of 
air d'isaharged per mdnute. Take the relation between px 
and liw Sit 60 degrees as 12 px = IQ X .433 hw; also, A X i^ = 
144 Q' when Q' = cubic feet of air discharged pe.r second 
and, from formula 54, liw = v- -^ 435 6. Then by substituting 
in formula 56 

3.75 X .577 X v^ X 144 Q' 

H. P. = = .0000022 i;2 Q' (57) 

4356 X 33000 

Application 1. — Let the effective area of a stream of dry 
air at 60 degrees, exhausting between the pressures of pn = 
iy2 ounces and p = ^/^ ounce, be 400 square inches. What is 
the work performed per minute and the horse-power con- 
sumed? (For velocity see second column Table XX). 

W = 3.75 X (11/^ — V2) X 400 X 87 = 130500 foot pounds, 
and H. P. = .000114 X (IVs — 1/2) X 400 X 87 = 3.96. 

Application 2. — A fan is delivering 1000000 cubic feet of 
ajir per hour to a heating system with a pressure of % 
ounce. What is the theoretical horse-power of the fan? 
H, P. = .0000022 X (74.5)2 ^ 277 =:= 3.38 

127. Actual Horse-Power Cousuiued in 3Ioving Air by 
BloT\'er Fans: — The theoretical horse-power of a fan is that 
horse-power necessary to move the air. This amount is al- 
ways exceeded, however, because of the inefficiency of the 
blowe.r. Let E = efficiency of the blower, then formulas 60 
and 61 become 

.000114 Px A V 

n. p. = . (58) 



.0000022 V2 Qf 

n. p. = (59) 



194 HEATING AND VENTILATION 

The value of E varies with the peripheral velocity and 
the percentage of free outlet. When subjected to ordinary 
service, the efficiency of the fan or blower may vary any- 
where from 10 to 40 per cent. Probably a safe figure, for 
an efficiency not definitely known, is 30 per cent, for cen- 
trifugal fans in heating systetms. Later improved types, 
such as the Sirocco and Multivane fans, will be found from 
40 per cent, to 60 per cent, efficient. See also Art. 1.31. 

128. Carpenter's Practical Rules: — ^Many experiments 
have been run upon blower fans to determine their capacity 
in cubic feet of adr delivered per minute and to determine 
the horse-power necessary to move this air. Probably as 
satisfactory as any are the rules quoted by Prof. Carpenter 
in H. & V. B., Art. 162, as follows: 

Rule. — ''The capacity of fans, expressed in cubic feet of air de- 
livered per minute, is equal to the cube of the diameter of the fan 
ivheel in feet multiplied by the number of revolutions, multiplied by 
a coefficient having the folloioing approximate value : for fan with 
single inlet delivering air without pressure, 0.6; delivering air loith 
pressure of one inch, 0.5; delivering air loith pressure of one ounce, 
0.4; for fans with double inlets, the coefficient should be increased 
al>out 50 per cent. For practical purposes of ventilation, the ca- 
pacity of a fan in cubic feet per resolution will equal .4 the cube 
of the diameter in feet.'' 

Rule. — ''The delivered horse-power required for a given fan or 
blower is equal to the 5th power of the dia^neter in feet, multiplied 
by the cube of the number of revolutions per second, divided by one 
million and multiplied by one of the folloiving coefficients : for free 
delivery, 30; for delivery against one ounce pressure, 20; for de- 
livery against two ouyices of pressure, 10." 

The two above rules stated as formulas are as follov/s: 



3 I Cu. ft. of air per min. 

D = J ■ (60) 

\ C X R. P. M. 

where D — the diameter in feet and C = the coefficient, .4 
for pressure of one ounce, .5 for pressure of one inch, and 
.6 for no pressure. 

D^ (R. P. S.)^ X C. 
E. P. = (CI) 

1000000 

where C = 30 for open flow, 20 for one ounce and 10 for two 
ounces pressure respectively. These two rules may be 



PLENUM WARM AIR HEATING 



195 



checked up by sizes obtained from catalogs. They give, 
however, in ordinary calculations, very close approxima- 
tions. 

Note. — ^In using formula 60 foT Sirocco or Multivane 
fans, the coefficient, C, becomes 1.1, 1.2 and 1.3 respectively. 
Likewise, for formula 61 it becomes 100, 95 and 90 respec- 
tively. 

129. If it is Desired to Obtain the Approximate Sizes of 
the Diflferent Parts of the Fan AVheel and Opening, the same 
can be found by the following table which gives good aver- 
age values for steel pLate fans. For -more complete data 
see tables in catalogs, 

TABLE XXIII.* 



Diameter wheel 




D 






Diameter inlet, single 


.66 D 






Diameter inlet, double 


.50 D 






Dimensions of exhaust 


.60 D 


X 


.50 D 


Width of wheel at outer circumference 


.50 D 


to 


.60 D 


Least radial distance from wheel to casing 


.08 D 


to 


.16 D 


Maximum radial distance from wheel to 










casing 


.50 D 


to 


1.00 D 


Least side distance from wheel to casing 


.0 


5 D 


to 


.08 D 






Discharge vert 




Discharge 


horiz. 


Occupied space 














of 


Length 


1.7 D 






1.5 


D 


full-housed fan 


Width 


.7 D 






.7 


D 




Height 


1.5 D 






1.7 


D 



*This table does not apply to Sirocco or Multivane fans. 

130. Fan Drives: — Fans for heating and ventilating 
purposes, may be driven 'by simple horizontal or vertical, 
throttling or automatic steam engines, or by electric mo- 
tors; the principal advantage of the latter being the clean- 
liness. In either case the power may be direct-connected 
or belt-connected to the fan. Direct-connected fans make 
a very neat arrangement, but they require slow speed 
engines or motors, occasionally making them so large as to 
be prohibitive. Where engines are used, any unusual noise 
or pounding in the parts is frequently carried through the 
fan to the air current and up to the rooms. Belted drives 
may run at higher speeds but they must of necessity be set 
of£ from the fan ten feet or more to get good belt contact. 



196 HEATING AND VENTILATION 

Chain drives that are fairly quiet in operation will permit 
the same reductions of speed and will allow the engine to 
be set very close to the fan. Where a reduction is made in 
the space between the engine and the fan, it had best be 
made in the last named way. 

In deciding between an engine drive and a motor drive 
for use with steam coils, the amount of steam used in the 
engine should not be considered a loss, since this is all 
exhausted into the heater coils and is used instead of live 
steam from the boilers. An engine of high efficiency is not 
so essential either, unless the exhaust steam cannot be 
used. Enclosed engines running in oil are preferred when 
used on high speeds. The belt when used should, if pos- 
sible, have the tight side below to increase the arc of 
contact. 

Electric motors have more quiet action and in special 
cases should be specified. They would generally be speci- 
fied for installations where the exhaust steam could not 
be used, as in systems for ventilating only. This method of 
driving the fan is more satisfactory in many ways but its 
operation is usually more expensive. Direct current motors 
are desirable, whenever they can be applied, because of the 
convenience in obtaining changes of speed and because the 
motors may easily be direct-connected to the fan. Alter- 
nating current motors are used but they usually run at 
higher speeds, requiring reduction drives and are not so 
satisfactory in regulation. Speed reductions of 40 per cent, 
may be had with alternating current machines where Te- 
quired. 

131. Speed of the Pan: — A blower fan, exhausting into 
the open air, will deliver air with a linear velocity slightly 
below the peripheral velocity of the fan blades, but if this 
same fan be connected to a system of ducts and heater 
coils, the linear velocity of the air becomes much less be- 
cause of the increased resistance and the Jag or slip that 
takes place between the fan blades and the moving air. In 
the average heating system this slip may be as great as 
40 to 50 per cent. See Art. 127. It is customary, therefore, 
in applying blowers to heating systems, to consider the 
linear velocity of the air as it leaves the fan to be one- 
half that of the periphery of the fan blades. Since the 
velocity of the air upon delivery from the fan should not 
exceed 1800 to 2500 feet per minute, the outer point on the 



PLENUM WARM AIR HEATING 



197 



fan blades should not be expected to move faster than 3600 
to 5000 feet per minute. Knowing this peripheral velocity, 
the revolutions per minute may be selected and the diameter 
obtained. 

In all direct-connected fans the revolutions per minute 
must agree with that of the engine or motor. In belted fans, 
however, this restriction need not apply. It is found that 
ordinary blower fans running at high speeds are very noisy 
and so practice has determined largely the number of revo- 
lutions to use. Speeds used by the American Blower Com- 
pany in the latest type of Sirocco fan are given in the fol- 
lowing table. 

TABLE XXrV. 

Speeds of Blower Fans in R. P. M. 



Diameter of 




Differential pressures. 




wheel in 
inches. 








1-2 oz. 


3-4 oz. 


loz. 


1 1-2 oz. 


2oz. 


18 


5S8 


660 


762 


933 


1076 


24 


404 


495 


572 


700 


807 


33 


269 


330 


381 


466 


638 


48 


202 


248 


286 


350 


403 


60 . 


161 


198 


228 


280 


322 


72 


131 


165 


190 


233 


269 


84 


115 


142 


163 


200 


231 


90 


107 


132 


152 


18G 


214 



In the recent developments for blower fans the num- 
ber of blades is increased and the depth of the blades is 
diminished, making the operation of the fan somewhat sim- 
ilar to that of the steam turbine. These fans seem to de- 
velop a much higher efficiency under tests than the ordi- 
nary paddle wheel fan. As a result, the diameter of the 
w.heel may be smaller with the same revolutions for a given 
work or the wheel may have the same diameter with a re- 
duced speed for a given work. Tables 50, 51 and 52, 
Appendix, give a summary of the latest catalog data. 

132, Size of the Engine: — In obtaining the size of the 



198 HEATING AND VENTILATION 

engine, it will be necessary first to assume the horse-power. 
This had better be taken as a certain ratio to that of the 
fan. Probably a safe value would be 

H, P. of the engine = | H. P. of the fan (62) 

Having obtained the horse-power of the engine, it will 
next be necessary to find the size of the cylinder. Let pa = 
the absolute initial pressure of the steam in the cylinder, 
i. e., atmospheric pressure + gage pressure, and r = number 
of the steam expansions in the cylinder, i. e., reciprocal of 
the per cent, of cut-off. The cut-off allowed for high speed 
engines in economical power service, approximates 25 per 
cent, of the stroke, but in engines for blower work this 
may be taken at 50 per cent, or half stroke. Find the 
mean effective pressure, pi, by the formula 

1 + hyperbolic logarithm of r 

Pi = Pa —- — back pressure (63) 

r 

Next, let I = length of the stroke in inches and N = number 
of revolutions per minute and apply the formula 

2 p^ I A N 
H.P.— (64) 

12 X 33000 

and find A, the area of the cylinder, from which obtain d, 
the diameter of the cylinder. In applying formula 64 it 
will be necessary to assume I. This, for engines operating 
blowers, may be taken 

2 Z 2V^ =: 200 to 400 

Formula 63 assumes that the steam in the cylinder expands 
according to the hyperbolic curve, pv z= p'v'. For values 
of hyperbolic or Naperian logarithms see Table 5, Appendix. 
It also assumes no loss in the recompression of 
the steam in the cylinder. Both assumptions are only 
approximately correct, but the errors are slight and to a 
certain degree, tend to neutralize each other, hence the 
final results from this formula are near enough to be used 
for approximate calculations. For such work as this, r 
may be taken from 2 to 3, the former being probably pre- 
ferred. The back pressure should not be taken higher than 
5 pounds gage (19.7 pounds absolute), since this is deter- 
mined by the pressure in the coils carrying exhaust steam. 
This pressure, in ordinary service, drops nearly to atmos- 
pheric pressure. 



PLENUM WARM AIR HEATING 19» 

lln finding" the dianaeter and length of the stroke of the 
cylinder, it may 'be necessary to make two or more trial 
a'pplications before a good size can be obtained. Owing 
to the fact that the initial steam pressure is frequently 
low, say not to exceed 40 or 50 pounds, the mean effective 
pressure is small, thus calling for a cylinder of large 
diameter. In such cases, the diameter of the cylinder may 
be greater than the length of the stroke. In cases where 
high pressure steam is used, say 100 pounds gage, the 
diameter of the cylinder would be less than the length of 
the stroke. 

APPLICATI0^- 1. — ^Assume the following to fit the desig-n 
shown in Figs. 104, 105 and 106: good dry steam from the 
boiler to the engine at 100 pounds gage pressure; direct- 
connected engine to fan, running at 180 revolutions per 
minute and delivering 2000000 cubic feet of air per hour 
to the building; steam cut-off in the cylinder at one-third 
stroke and used in the coils at 5 pounds gage pressure; 
find the sizes and horse-powers of the fan and engine unit. 
Applying formulas 60, 61, 62, 63 and 64 



V 



2000000 

D. of fan = ^/ = 5.5 feet. 

60 X 1.1 X 180 



(5.5)5 X (3)3 X 87 

H. P. of fan = = 11.8 

1000000 

Check the fan size and horse-power by Table 52, Appendix. 
H. P. of Engine = A x 11.8 = 15.7 

o 

/ 1 + 1.0986 \ 
Pi = 115 f j — 19.9 = 60.5 pounds per 

250 

square inch. Now if 2 I N = 250, then 7 = = .69 feet = 

360 

15.7 X 12X 33000 

8.25 inches and A = ^- = 34.5 square 

2 X 60.5 X 8.25 X 180 

inches = 6.625 inches diameter. The engine would be 6.625 
inches X 8.25 inches, at 180 R. P. M. 

Application 2. — Assuming the values as in application 1, 
excepting that the steam is taken from a conduit main 
under a pressure of, say 30 pounds per square inch gage, 
that 2 I N = 300, and that the steam cut-off in the cylinder 
Is at one-half stroke. Then, as before, D of fan = 5.5 feet; 



200 HEATING AND VENTILATION 

E. P. of fan = 11.7; and n. P. of engine = 15.7; the mean 
effective pressure is, however, 

1 + .6931 
Pi r= 45 / ) — 19.9 = 18.2 pounds per sq. In. 



V 2 / ~ 



15.7 X 12 X 33000 

and A = = 95 square inches. 

2 X 18.2 X 10 X 180 

Size of engine would be 11 inches X 10 inches, at 180 
R, P. if. 

133. Piping Connections around Heater and En^ne: — 

"Where the fans are run by steam power it is considered 
best to reduce the pressure of the steam by a pressure re- 
ducing" valve before allowing the live steam to enter the 
coils. Where this reduction is made to 5 pounds or below, 
it may be entered into the same main with the exhaust 
steam from the engine, if desired; the back pressure valve 
on the exhaust steam line providing an outlet to the at- 
mosphere in case the pressure should run above the 5 
pounds allowable back pressure. If the value of the back 
pressure is increased much above 5 pounds, the efficiency 
of the engine is seriously affected. In many installations 
where the condensation from the live steam is desired free 
from oil, a certain number of coils are tapped for exhaust 
steam and this condensation trapped to a waste or sewer, 
the other coils delivering to a receiver of some sort for 
boiler feod or other purposes as may be required. 

Every system should be fully equipped with pressure 
reducing valves, back pressure valves, traps and a sufficient 
numlber of globe or gate valves on the steam supply, and of 
gate valves on the returns to make the system flexible and 
responsive to varying demands. Figs. 102 and 103 show a 
typical plan and elevation for such connections. Some en- 
gineers advocate lifting the returns about 20 or 30 inches 
as shown at A and B to form a water seal for each sec- 
tion, thus making them independent in their action. This, 
in some cases where the coils are very deep, would be a 
benefit. 

134. Application to School Building: — The three follow- 
ing figures and summary show the results of an applica- 
tion of the above to a school building. The summary, 



PLENUM WARM AIR HEATING 



201 



Table XXV, gives in compact form such calculated resultss 
as admit of .tabulation. Most of the applications through- 
out Chapters X, XI and XII, also refer to this same building. 
The plans show the double-duct system, with plenum 
chamber and ducts laid just below the basement floor. The 
small arrows show the heat registers and vent registers for 
each room. The same stack which served as a heat car- 



\ 

0TRAP 



aaCK Pf?E55URC 
VALVE 



«M-«iW- 



O STEAM SEPAWVTOR 



'PRESiREttvftLVE 



Fig. 102. 



TO ATMOSPHERE 

BftCK PRr55UflE VMVE 



11 ^ 



J 



,PflE55URE REOuCiNC 
vAIVE-lVE 5TEAM 



^ GATE Ws-^^^^ 'kav 

Fig. 103. 






rier to the room on one floor serves as the vent stack 
for the corresponding room on the floor above, there being 
a horizontal cut-off between them. The cut-off at the heat 
register should be so curved as to throw the current of 
heated air into the room with the least possible friction or 
eddy currents, as shown in Fig. 22. 



202 



HEATING AND VENTILATION 



TABLE XXV. 

Data Sheet for Figs. 104, 105, 106. 



Room 


n 


Heat loss in B.-t .u. per 
hour from room not 
counting ventilation 


>< 

d 

•rH 

d 

§ 

o 
m 

as 


1 

-1-3 

d 
o 
o 
u 

Ph 


Cubic feet of air needed 
per hour as a heat 
carrier 


1 

02 

d 

£ 



6 


II 
=1 

4^ d 
u 

--H OJ 

1^ 


d 

2 

•rH 

■faD 
0) 


03 

o 

d 

hH 

d 

•rH 

M 

4J 
QQ 


1 


1 

\^ 

VA 
VA 

"ilV 
VA 

VA 


51,520 

74,200 
29,400 
36,260 
42,210 
35,350 

16^520 
16,520 
42,210 






40,185 
57,876 
22,932 
28,283 
32,923 
27,573 

i2"885 
12,885 
32,923 


2 

i' 

1 
1 
1 

i" 

1 
1 


322 

181 
226 
263 
220 

103 
103 
263 


13x20 

17x18 
17x21 
17x25 
17x21 

"13x13 
13x13 

17x25 


13x13 


2 








8 






17x13 


4 






17x13 


5 






17x13 


6 






17x13 


7 

8 

9 






1*3x8 
13x 8 


10 






17x13 










Totals. 




344,190 






268,466 











11 


1 

VA 

VA 

VA 

VA 

1 

IH 

VA 

VA 


81,130 
115,430 
40,500 
55,370 
63,840 
48,440 
51,940 
23,660 
23,660 
63,840 






63,281 
99,039 
31,775 
47,507 
54,775 
39,672 
40,513 
19,377 
18,455 
49,795 


2 
4 
1 
2 
2 
1 
2 
1 
1 
2 


506 
792 
278 
380 
438 
317 
324 
155 
148 
398 


17x24 
17x18 
17x26 
17x18 
17x21 
17x30 
13x20 
13x20 
13x20 
17x18 


17x13 


12 

13 

14 

15 

16 

17 


126,973 
44,583 
60,907 
70,221 
50,862 


10 
10 
10 


17x13 
17x13 
17x13 
17x13 
17x13 
13x13 


18 

19 

20 


24,843 


5 


13x13 
13x13 
17x18 


Totals. 




540,100 






467,189 









21 


M 


81,130 
17,150 
103,460 
17,150 
31,900 
48,580 
93,030 
28,420 
37.380 
54,110 






68,281 
13,877 
88,764 
13,877 
27,447 
41,682 
79,819 
22,163 
29,156 
42,206 


2 
1 
2 
1 
1 
2 
2 
2 
1 
2 


5r6 

107 
710 
107 
220 
833 
638 
177 
233 
888 


17x24 
13x13 
21x28 
13x18 
17x21 
18x20 
17x30 
18x15 
17x21 
13x20 


17x13 


22 






13x 8 


23 

24 


113,800 


10 


17x13 
13x 8 


25 

26 

27 

28 


35,189 

53,488 

102,333 


10 
10 
10 


17x13 
13x13 
17x13 
13x 8 


29 






17x13 


80 






13x13 


Totals. 




598,961 






421,272 











Vent registers taken same size as heat registers. For sizes of 
engine, fan, heater coils, etc., see applications un(ier these heads 



PLENUM WARM AIR HEATING 



203 



O tn ft 




204 



HEATING AND VENTILATION 




Fig-. 105. 



PLENUM WARM AIR HEATING 



205 





'- t=l t=l t=i 


f=< 


k=^ 


t=^ 


^t=^ ,=^ „ 


. , 




c 




3 




fit 




c 




D 


L 




I 


^c 






L 




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H s h-^ « 




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♦- □ 




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I 


n t=J l=! MdoH '=' ^ 


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— ,° - 
1 . 


■ / 


- 


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L 


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i 




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' F 




_^ 


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^ 












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i 


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I 


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t 




-ryrO 


7 


oo_^_ 




L 


I 






\ 


~ 


I 


r^ 




a o 




o 




D td t=d bdQDbd UJ t=J 




T 

1 


' 


1 




o 






J 




3 




! 




I 




c 
o 


I 


T 
1 






















I 




1 










[ § 








B 








y \ 


- 


11 
I I 


















«— r 






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f=^ F=! ^ 


t=l NH M 


1=1 td 1=1 



Ilg. 106. 



206 HEATING AND VENTILATION 



REFERENCES. 



References on Mechanical AVarm Air Heating. 



Technical Books. 

Snow, Furnace Heating, p. 99. Monroe, Steam Heat, d Vent., 
p. 124. Carpenter, Heating and Yentilating Buildings, p. 333. 
Hubbard, Poiccr, Heating and Ventilation, pages 525 and 551. 



Techxical Periodicals. 

Engineering Review. Ventilating* and Air Washing" Appar- 
atus Installed in the Sterling-Welch Building, Cleveland, 
O., Jan. 1910, p. 38. Steam Heat, and Vent. Plant Required 
for Addition to the Hotel Astor, New York, March 1910, p. 
27. Heating and Ventilating Plant of the Boston Safe De- 
posit and Trust Company's Building, C. L. Hubbard, April 
1910, p. 37. Heating and Ventilating Installation on the 
Burnet St. School, Newark, N. J., Jan. 1909, p. 20. Heating 
and Ventilating the New Jersey State Reformatory, Sept. 
1909, p. 27. Comparison of Heat, and Vent. Plants Installed 
in Chicago Schools and Buildings at Various Periods, T. J. 
Waters, June 1906, p. 14. Heating and Ventilating of 
Schools, F. G. McCann, June 1906, p. 11. The Heating and 
Ventilation of Schools, Dec. 1904, p. 1; March 1905, p. 4; 
Sept. 1905, p. 1; Oct. 1905, p. 5. Note: — The last two articles 
taken together comprise a complete series of the heating 
and ventilating of the schools of New York City. Machinery. 
Fans, C. L. Hubbard, Oct. 1905, p. 49; Nov. 1905, p. 109; 
Dec. 1905, p. 165. Heaters for Hot Blast and Ventilation, 
C. L. Hubbard, March 1907, p. 353. The Heating and Ven- 
tilation of Machine Shops, C. L. Hubbard, Sept. 1907, p. 1. 
Heating and Ventilating Offices in Shops and Factories, C. 
L. Hubbard, Feb. 1910, p. 437. Fans, Machinery's Reference 
Series, No 39. The Heating and Yentilating Magazine. Figuring 
Flow of Air in Metal Pipes by Chart, B. S. Harrison, Dec. 
1905, p. 1. Flow of Air in Metal Pipes, J. H. Kinealy, July 
1905, p. 3. Friction of Bends in Air Pipes, J. H. Kinealy, 
Sept. 1905, p. 1. A Test of Hot Blast Heating Coils, March 
1905, p. 1. Simplifying the Installation and Operation of 
School Heating and Ventilating Apparatus, S. R. Lewis, July 
1908, p. 10. A Rational Formula Covering the Performance 
of Indirect Heating Surface, Perry West, March 1909, p. 1. 
Charts Showing the Performance of Hot Blast Coils, B. S. 
Harrison, Oct. 1907, p. 23. Loss of Pressure in Blowing Air 
through Heater Coils, with New Formula, E. M. Shealy, 
Nov. 1911. The Engineering Magazine. Modern Systems for 
the Ventilation and Tempering of Buildings, Percival R. 
Moses, Feb. 1908. Domestic Engineering. Practical Sugg'es- 
tions about Blower Systems for Shop Heating, F. R. 
Still, Vol. 46. No. 4, Jan. 23, 1909, p. 100; Vol. 46, No. 
5, Jan. 30, 1909, p. 125. Trans. A. S. H. d V. E. Supplementing 
Direct Radiation by Fans, Vol. X, p. 286. Methods of Test- 



PLENUM WARM AIR HEATING 207 




iCU(, p. XOO. JT Ci J-Ui lllCLlilJC U-L XIUL JJlcXaL XXCCLLXXl^ K^yjLl^, UO-IX. 

28, 1905. Some Features of Indirect Heating-, May 27, 1905. 
Heating- and Ventilating- in the Carnegie Residence, N. Y., 
Oct. 3, 1903, Vol. 48, p. 403. Ventilating- and Heating the 
Rochester Athenaeum & Mechanics Institute, July 19, 1902, 
Vol. 46, p. 60. Poiccr. Horse-Power of a Fan Blower, Alibert 
E. Guy, June 13, 1911. Heating and Ventilating- System of 
the Ritz-Carlton Hotel, Charles A. Fuller, Mar. 19, 1912. 
Ventilating System for Small Schools, Charles A. Fuller, 
Dec. 10, 1912. 



CHAPTER XIIL 



DISTRICT HEATING OR CENTRALIZED HOT WATER 
AND STEAM HEATING. 



GENERAL. 



135. Heating Residences and Business Blocks from a 
central station is a method that is being- employed in' many 
cities and towns throughout the country. The centralization 
of the heat supply for any district in one larg-e unit has an 
advantage over a number of smaller units in being able to 
burn the fuel more economically, and in being able to re- 
duce labor costs. It has also the advantage, when in con- 
nection with any pow^^er plant, of saving the heat which 
would otherwise g"0 to waste in the exhaust steam and stack 
gases, by turning it into the heating" system. The many 
electric lighting and pumping stations around the country 
give large opportunity in this regard. Since the average 
steam power plant is very wasteful in these two particulars, 
any saving that might be brought about should certainly be 
sought for. On the other hand, however, a plant of this 
kind has the disadvantage in that it necessitates transmit- 
ting the heating medium through a system of conduits, which 
generally is a wasteful process. The failure of many of the 
pioneer plants has cast suspicion upon all such enterprises 
as paying investments, but the successful operation of many 
others shows the possibilities, where care is exercised in 
their design and operation. 

136. Important Considerations in Central Station Heat- 
ing: — In any central heating system, the following consider- 
ations will go far towards the success or the failure of the 
enterprise: 

First. — There should be a demand for the heat. 

Second. — The plant should be near to the territory heated. 

Third. — There should be good coal and water facilities at 
the plant. 

Fourth. — The quality of all the materials and the instal- 
lation of the same, especially in the conduit concerning in- 



DISTRICT HEATING 209 

sulation, expansion and contraction, and durability, are 
points of unusual importance. 

Fiftli. — The plant must be operated upon an economical 
basis, the same as is true of other plants. 

tiixtli. — The Joad-factor of the plant should be high. This 
is one of the mo-st important points to be considered in com- 
bined heating and power work. The greater the proportion 
of hours each piece of apparatus is in operation, to the total 
number of hours that the plant is run, the greater the plant 
efficiency. The ideal load-factor requires that all of the ap- 
paratus be run at full load all the time. 

The average conduit radiates a great deal of heat, hence, 
the nearer the plant to the heated district the greater the 
economy of the system. Likewise a location near a railroad 
minimizes fuel costs, and good water, with the possibility 
of saving the water of condensation from the steam, assists 
in increasing fthe economy of the plant. It is to be expected 
that even a well designed plant, tmless safeguarded against 
ills as above suggested, would soon succumb to inevitable 
failure. 

Two types of centralized heating plants are in use, Tioi 
ijcater and steam. Each will be discussed separately-. In the 
discussion of either system, certain definite conditions will 
have to be met. First of all, there should be a demand in 
that certain locality for such a heating system, before the 
plant can be considered a safe investment. To create a de- 
mand requires good representatives and a first-class resi- 
dence or business district. When this demand is obtained 
the plan of the probable district to be heated will first be 
platted and then the heating plant w^ill be located. In many 
cases the heating plant will be an added feature to an al- 
ready established lighting or power plant and its location 
will be more or less a predetermined thing. 

In addition to these material and financial features just 
mentioned, one must consider the legal phases that always 
come up at such a time. These relate chiefly to the franchise 
requirements that must be met before occuping the streets 
with conduit lines, etc. All of these considerations are a 
part of the one general scheme. 

137. The Scope of tlie Work in central station heating 
may be had from the following outline: 



210 



HEATING AND VENTILATION 



Central Sta- 
tion Heating^ 



Hot Water Heating 
by use of 



Exhaust steam heaters 
Live steam heaters 
Heating boilers 
Economizers 
Injectors or 
Com-minglers 



Steam Heating J Exhaust steam 

\Live steam 



In the 7wt water system the return water at a lowered tem- 
perature enters the power plant, is passed through one or 
more pieces of apparatus carrying live or exhaust steam, or 
flue gases, and is raised in temperature again to that in the 
outgoing main. Prom the above, a number of combinations 
of reheating can be had. Any or all of the units may be put 
in one plant and the piping system so installed that the 
water will pass through any single unit and out into the 
main; or, the water may be split and passed through the 
units in parallel; or, it may be made to pass through the 
units in series. All of these combinations are possible, but 
not practicable. In most plants, two or three combinations 
only are provided. In the existing plants the order of pref- 
erence seems to be, exhaust steam reheaters, economizers, 
heating boilers, injectors or com-minglers, and live steam 
heaters. 

All of the above pieces of reheating apparatus operate 
by the transmission of heat through metal surfaces, such as 
brass, steel or cast iron tubes, excepting the com-mingler, 
this being simplj^ a barometric condenser in which the exhaust 
steam is condensed by the injection water from the return 
main, the mixture being drawn directly into the pumps. 

The objection to the tube transmission is the lime, mud 
and oil deposit on the tube surfaces, thus reducing the rate 
of transmission and requiring frequent cleaning. The ob- 
jections to the com-minglers are, first, that the pump must 
draw hot water from the condenser and second, that a cer- 
tain amount of the oil passes into the heating line. With 
perfected appai^atus for removing the oil, the com-mingler 
will no doubt supersede, to a large degree, the tube re- 
Jieaters in hot water heating. 



DISTRICT HEATING 2ll 

In the steam system the proposition is very much simpli- 
fied. The exhaust steam passes through one or more oil 
separating devices and is then piped directly to the header 
leading to the outgoing main. Occasionally a connection is 
made from this line to a condenser, such that the steam, 
when not used in the heating system, may be run directly 
to the condenser. These pipe lines, of course, are all prop- 
erly valved so that the current of steam may easily be de- 
flected one way or the other. In addition to this exhaust 
steam supply, live steam is provided from the boiler and 
enters the header through a pressure reducing valve. In 
any case when the exhaust steam is insufficient the supply 
may be kept constant by automatic regulation on the reduc- 
ing valve. 

In selecting between hot water and steam systems the 
preference of the engineer is very largely the controlling 
factor. The preference of the engineer, however, should be 
formed from facts and conditions surrounding the plant, and 
should not come from mere prejudice. The following points 
are some of the important ones to be considered: 

First cost of plant installed. — This is very much in favor of 
the steam system in all features of the power plant equip- 
ment, the relative costs of the conduit and the outside work 
being very much the same in the two systems. 

Cost of operation. — This is in favor of the hot water sys- 
tem because of the fact that the steam from the engines 
may be condensed at or below atmospheric pressure, while 
the exhausts from the engines in the steam systems must 
be carried from five to fifteen pounds gage, which naturally 
throws a heavy back pressure upon the engine piston. 

Pressure in circulating mains. — This is in favor of the steam 
system. The pressure in any steam radiator will be only 
a few pounds above atmosphere, while in a hot water sys- 
tem, connected to high buildings, the pressure on the first 
floor radiators near the level of the mains becomes very 
excessive. The elevation of the highest radiator in tho 
circuit, therefore, is one of the determining factors. 

Regulation. — It is easier to regulate the hot water system 
without the use of the automatic thermostatic control, since 
the temperature of the water is maintained according to a 
schedule, which fits all degrees of outside temperature. 



212 HEATING AND VENTILATION 

T^^en automatic control is applied, this advantage is not so 
Kiarked. 

Returning the water to the poicer plant. — In most steam plants 
the water of condensation is passed throug-h indirect heaters, 
to remove as much of the remaining- heat as possible and 
ds then run to the sewer. This procedure incurs a consider- 
a;ble loss, especially in cold weather when the feed water 
at the power plant is heated from low temperatures. This 
point is in favor of the hot water system. 

Estimating charges for heat. — This is in favor of the steam 
system since, by meter measurement, a company is able to 
apportion the charges intelligently. The flat rate charged 
for water heating and for some steam heating is in many 
cases a decided loss to the company. 

138. Conduits: — In installing conduits for either hot 
water or steam systems the selection should be made after 
determining, first, its efficiency as a heat insulator; second, 
its initial cost; third, its durability. Other points that must 
be accounted for as being very essential are: the supporting, 
anchoring, grading and draining of the mains; provision for 
expansion and contraction of the mains; arrangements for 
taking off service lines at points where there is little move- 
ment of the mains; and the draining of the conduit. 

Some conduits may be installed at very little cost and 
yet may be very expensive propositions, because of their in- 
ability to protect from heat losses; while, on the other hand, 
some of the most expensive installations save their first 
cost in a couple of years' service. Many different kinds of 
insulating materials are used in conduit work such as mag- 
nesia, asbestos, hair felt, wool felt, mineral wool and air cell. 
Each of these materials has certain advantages and under 
certain conditions would be preferred. It is not the real 
purpose here to discuss the merits of the various insulators, 
because the quality of the workmanship in the conduit en- 
ters into the final result so largely. The different ways that 
pipes may be supported and insulated in outside service will 
be given, with general suggestions only. Fig. 107 shows a 
few of the many methods in common use. A very simple 
conduit is shown at A. This is built up of wood sections 
fitted end to end, then covered with tarred paper to prevent 
surface water leaking in and bound with straps. The pipe 
either is a loose fit to the bore and rests upon the inner sur- 



DISTRICT HEATING 213 

face, or is supported on metal stools, driven into the wood or 
merely resting upon it. These stools hold the pipe concen- 
tric with the inner bore of the log". With much movement 
of the pipe endwise, from expansion and contraction, these 
stools should not be used unless they are loose and have a 
wide surface contact with the wood. A metal lining- with 
the pipe resting directly upon it is considered good. The 
conduit is laid to a good straight run in a gravel bed and 
usually over a small tile drain to carry off the surface water, 
excepting as this drain is not necessary in sections where 
there is good gravel drainage. The insulation in A is only 
fair. The air space around the pipe, however, is to be com- 
mended. B is an improvement over A and is built up of 
boards notched at the edges to fit together. The materials 
used, from the outside to the center, are noted on the sketch 
beginning with the top and reading down. This covering is 
in general use and gives good satisfaction from every stand- 
point. C shows a good insulation and supports the pipe 
upon rollers at the center of a line of halved, vitrified tile. 
The lower half of the tile should be graded and the pipe then 
run upon the rollers, after which it may be covered with 
some prepared covering and the remaining space next the 
tile filled with asbestos, mineral wool or other like material. 
D shows the same adapted to cellar work. Occasionally two 
pipes are run side by side, main and return, in which case 
large halved tiles may be used as in E, having large metal 
supports curved on the lower face to fit the tile. If these 
supports are not desired the same kind of straight tiles may 
be used with a tee tile inserted every 8 to 12 feet having the 
bell looking down as in F. In this bell is built a concrete 
setting with iron supports for the pipes which run on rollers, 
over a rod. These rollers are sometimes pieces of pipes cut 
and reamed, but are better if they are cast with a curvature 
to fit the pipes to be supported. This form of conduit, when 
drained to good gravel, gives first-class service. G, H and / 
show box conduits with two or more thicknesses of % inch 
boards nailed together for the sides, top and bottom. The 
bottom of the conduit is first laid and the pipe is run. The 
sides are then set in place and the insulating material put 
in, after which the top is set and the whole filled in. / shows 
the best form of box, since with the air spaces this is a 
very good insulator. All wood boxes are very temporary, 
hence, brick and concrete are usually preferred. -K is a 



214 



HEATING AND VENTILATION 







GRAVEL - 
PUMP LOG 
5T00L5 

PIPE ■ 

DRAIN 







A 



GRAVEL 
ABPHALTUM 

WOOD 
COR PAPER 
ASBESTOS 
TIN LINING -, . 

IN WOOL — 1^ 



PIPE 
ROLLER 




WOOD 
TILE 

MIN. WOOL- 
SECTIONAL 
COVERING^ 
PIPE 
ROLLER 



' ^^\\^<^^ \ ^ -fxr^ 



GRAVEL 

TILE , 
MIN WOOL 

PIPE 

IPE 5UPP. 
ON CRETE 

DRAIN 




Fig. 107a. 



DISTRICT HEATING 



215 



1 fcA^^i^::^^^»>v ^Y^^^^^^ ^'"^^^^^^■^''''J ' "'■'\ 




mmmmm^ 



m 






&^fLs:/j^-^^4:i%s4Myyj ^ 




M 



Fig. 107b. 



216 HEATING AND VENTILATION 

conduit with 8 inch brick walls covered with flat stones or 
halved g-lazed tiles cemented to place to protect from sur- 
face leakage. The bottom of the conduit has supports built 
in every 8 to 12 feet, and between these points the conduit 
drains to the gravel. The usual rod and roller here serve 
as pipe supports. The pipe is covered with sectional cover- 
ing- and the rest of the space may or may not be filled with 
wool or chips, as desired. L shows the sectional covering 
omitted and the entire conduit filled with mineral wool, hair 
'felt or asbestos, and ashes. M has the supporting rod built 
into the sides of the conduit and has the bottom of the con- 
duit bricked across and cemented to carry the leaks and 
drainage to some distant point, ^^ shows a concrete bot- 
tom with brick sides, having the pipe supported upon cast 
iron standards. The latest conduit has concrete slabs for 
bottom and sides and has a reinforced concrete slab top. 
This comes as near being permanent as any, is reasonable 
in price, and when the interior is filled with good non-con- 
ducting material, or when the pipe is covered with a good 
sectional covering, it gives fairly high efficiency. 

All conduits should be run as nearly level as possible 
to avoid the formation of air and water pockets in the main. 
Any unusual elevation in any part of the main may require 
an air vent being placed at the uppermost point of the curve, 
otherwise air may collect in such quantities as to retard cir- 
culation. All low points in the steam lines must be drained 
to traps. 

The heat lost from conduits is an item of considerable im- 
portance. A good quality of materials and insulation will 
probably reduce this loss as low as 20 to 25 per cent, of 
the amount lost from the bare pipe. To show the method of 
analysis and to obtain an estimate of the average conduit 
losses, the following application will be made to a supposed 
two-pipe hot water system. The loss of heat in B. t. u. per 
lineal foot from any pipe per hour may be taken from the 
formula 

Ec = KCA (t — f) (65) 

where K = rate of transmission for uncovered pipes, C = 100 
per cent. — efficiency of the insulation, A = area of pipe sur- 
face per lineal foot of pipe, t = average temperature in the 



DISTRICT HEATINa 



217 



inside of the pipe and f = average temperature on the out- 
side of the conduit. 

Application. — Having- given a system of conduit pipes 
(two pipes in one conduit) with sizes and lengths as stated 
in the first and second columns of Table XXVI, what is the 
probable heat loss in B. t. u. per hour on a winter day and 
what is the radiation equivalent in a hot w^ater system car- 
rying water at an average temperature of 170 degrees? 



TABLE XXVI. 



Pipe size 
inches 


Total lineal 

feet of main 

and return 


Surface per 

foot of length 

A 


B. t. u. per hr. 

per lineal foot 

He 


Equivalent 
no. of sq.ft. 
of H.W. Bad. 


2 


5000 


.62 


48.8 


1435 


3 


2000 


.91 


71.6 


842 


4 


3000 


1.06 


83.4 


1472 


6 


3000 


1.73 


137.1 


2420 


8 


2000 


2.26 


177.9 


2093 


10 


2000 


2.83 


221.9 


2611 


12 


2000 


3.33 


262.0 


3082 


1^ 


1000 


4.00 


314.8 


1852 



Totals. B. t. u. lost per hour 2687100 



1580? 



If K = 2.25, O = 100 — 75 = 25 per cent., t z= 175 and 
r = 35, we have for a 2 inch pipe, He = 2.25 X .25 X .62 X 140 
— 48.8, which for 5000 lineal feet = 244000 B. t. u., and for 
the entire system 2687100 B. t. u. If each square foot of hot 
water radiation gives off 170 B. t. u. per hour then the 
radiation equivalent for the 2 inch pipe is 244000 -^ 170 == 
1453 square feet. Similarly work out for each pipe size and 
obtain the values given in the last column of the table. This 
conduit loss is sufficient to heat 15807 square feet of radia- 
tion in the district. In terms of the coal pile it approxi- 
mates 350 pounds per hour. Now assuming the 14 inch 
main to supply the entire district at a velocity of 6 feet per 
second we have approximately 162000 square feet of H. W. 
surface on the line. From this the line loss is 15807-^162000 
=: 9.1 per cent. It should be remembered that the above as- 
sumes the plant working under a heavy load when the per 
cent, of line loss is a minimum. This loss remains fairly 



218 HEATING AND VENTILATION 

constant while the heat utilized in the district fluctuates 
greatly. In mild weather, therefore, the per cent, of line 
loss to the total heat transmitted is much greater. 

139. Layout of Street Mains and Conduits: — ^No definite 
information can be given concerning the layout of street 
mains, because the requirements of each district would call 
for independent consideration. The following general sug- 
gestions, however, can be noted as applying to any hot 
water or steam system: 

Streets to &e used. — Avoid the principal streets in the city, 
especially those that are paved; alleys are preferred because 
of the minimum cost of installation and repairs. 

Cutting of the mains. — Do not cut the main trunk line for 
branches more often than is necessary. Provide occasional 
by-pass lines between the main branches at the most im- 
portant points in the system, so that, if repairs are being 
made on any one line, the circulation beyond that point may 
be handled through the by-pass. Such by-pass lines should 
be valved and used only in case of emergency. 

Offsets and expansion jbints. — ^Offsets in the lines hinder 
the free movement of the water and add friction head to the 
pumps; hence, in water systems, the number should be re- 
duced to a minimum. Long radius bends at the corners re- 
duce this friction. Offsets are especially valuable to take 
up the expansion and contraction of the piping without the 
aid of expansion joints. This is illustrated in Fig. 108, where 
anchors are placed at A, and the gradual bending of the 
pipes at each corner makes the necessary allowance. The 
expansion in wrought iron is about .00008 inch per foot per 
degree rise in temperature; hence in a hot water main the 
linear expansion between 0° and 212° is .017 inch per foot of 
length or 1.7 inches for each 100 feet of straight pipe. In 
hot water heating systems, however, the temperature of this 
pipe would never be less than 50°, which would cause an 
expansion from hot to cold of only .013 inch per foot, or 
1.3 inches for each 100 feet of straight pipe. In a steam 
main the temperature may vary anywhere from 50° to 300°, 
making a linear expansion of .02 inch per foot of length or 2 
inches for each 100 feet of straight pipe. As here shown the 



DISTRICT HEATING 



219 



-'^ J ^ ,, 


A 


— °r^ 





S/- 



4 



Fig-. 108. 



movement from the anchor 
at A toward B may be ab- 
sorbed by the swing-ing" of the 
pipe about O. B.B. should 
therefore be as long- as possi- 
ble, say one full block, to 
avoid unduly straining- the 
pipe at the joints. Allowing a 
maximum movement of 6 
inches for each expansion joint, the anchors would be spaced 
500 and 300 feet center to center respectively, for hot water 
and steam mains. These figures would seldom be exceeded, 
and in some cases w^ould be reduced, the spacing- depending 
upon the type of expansion joint used. Ordinarily, 400 feet 
spacing" would be recommended for hot water and 300 feet 
for steam. If the city layout meets this value fairly well, 
then the expansion joints and anchors may be made to 
alternate with each other, one each to every city block. 

A few of the expansion joints in common use are shown 
in I" ig-. 109. A is the old slip and packed joint. This joint 
causes very little trouble except that it needs repacking 
frequently. It is very effective when properly cared for. 
The slip joint should have bronze bearing's on both the 
outside of the plug- and the lining of the sleeve. The ends 
of the plug and sleeve may be screwed for small pipes, 
or flanged for large ones. B shows an improved type of 
slip joint, having a roller bearing upon a plate in the 
bottom of the conduit, and plugs bearing against metal 
plates along the sides of the conduit to keep it in line. G 
and D show other slip joints very similar to A and B. C 
has one ball and socket end to adjust the joint to slight 
changes in the run of the pipe, and D has two packings 
enclosing the plug to give it rigidity. The drainage in 
each case is taken off at the bottom of the casting. E has 
two large flexible disks fastened to the ends of the pipe and 
separated from each other by an annular ring casting. 
These disks are frequently corrugated, are usually of cop- 
per and are very large in diameter so that the pipe has con- 
siderable movement without endangering the metal in the 
disks. F has a corrugated copper tube fastened at the ends 
to the pipe flanges. This is protected from excessive inter- 
nal pressure by a straight tube having a sliding fit to the 
inside of the flanges, thus allowing for end movement, O is 



220 



HEATING AND VENTILATION 











N 




\ 



r 




-^ 



u^— -T^^ 



12 




n 



lz.=z^^^^ 



t3 






Fig. 109. 



DISTRICT HEATING 



221 



very similar to E. It has, however, only one copper disk. 
This disk is enclosed in a cast iron casement, one side of 
which is lopen to the atmosphere, the other side having the 
same pressure as within the pipe. H is very similar to £7, 
having two copper diaphragms to take up the movement. 
These diaphragms flex over rings with curved edges and 
are thus protected somewhat against failure. / shows a 
copper U tube which is sometimes used. This is set in a 
horizontal position and the expansion and contraction is 
absorbed by bending the loop. In all these joints those 
which depend upon the bending of the metal require little 
attention except where complete rupture occurs. In old 
plants, however, the rupturing of these diaphragms is of 
frequent occurrence. The packed joint requires attention 
for packing several times in the year, but very seldom 
causes trouble other than this. 

Anchors. — In any long run of pipe, where the expansion 
and contraction of the pipe causes it to shift its position 
very much, it is necessary to anchor the pipe at intervals so 
as to compel the movement toward certain desired points. 
The anchor is sometimes combined with the expansion joint, 
in which case the conduit work is simplified. See Fig. 110. 




Fig. 110. 



222 



HEATING AND VENTILATION 



Service pipes to residences are taken off at or near the 
anchors. All condensation drains in steam mains are like- 
wise taken off at such points. 

Valves. — All valves on water systems should be straight- 
way g-ate valves. Valves on steam systems should be gate 
valves on lines carrying condensation, and renewable seat 
globe valves on the steam lines. Valves should be placed on 
the raain trunk at the power plant, on all the principal 
branch mains as they leave the main trunk, on all by-pass 
lines, on all the service mains to the houses, and at such 
im'portant points along the mains as will enable certain 
portions of the heating district to be shut off for repairs 
without cutting out the entire district. 

Manholes. — Manholes are placed at important points along 
the line to enclose expansion joints and valves. These man- 
holes are built of brick or concrete and covered with iron 
plates, flag stones, slate or reinforced concrete slabs. Care 
must be exercised to drain these points well and to have the 
covering strong enough to sustain the superimposed loads. 

140. Typical Design for Consideration: — In discussing 
district heating, each importa-nt part of the design work will 
be made as general as passible and will be closed by an 

















! 
















































1 

RES 

1 


IDENC 
1 


1 
E 

1 






1 











RESIDENCE 







1 






1 

1 


1 

1 










1 




1 




1 

; BUS 

: 1 


1 

INES5 
1 
























1 








' 1 






























>^ PLANT 







Fig. 111. 



DISTRICT HEATING 



223 



application to the following- concrete example which refers 
to a certain portion of an imaginary city, Fig*. Ill, as avail- 
able territory. A city water supply and lighting- plant Is 
located as shown, with lighting and power units aggregat- 
ing 475 K. TT., city water supply pumps aggregating 3000000 
gallons maximum capacity, and smaller units requiring ap- 
proximately 15 per cent, of the amount of steam used by 
the larger lighting units, all as suggested in general instruc- 
tions in the problem pamphlet. It is desired to re-design this 
plant and to add a district heating system to it; the same to 
have all the latest methods of operation and to be of such a 
size as to be economically handled. Fig. IIS shows the essen- 
tial details of the finished plant. 

141. Electrical Output and Exliaust Steam Available for 
Heating Purposes from the Povrer tTnits: — In the operation 
of such a plant, one of the principal assets is the amount of 
exhaust steam available for heating purposes. The amount 
may be found for any time of the day or night by construct- 
ing a power chart as in Fig. 112, and a steam consumption 
chart as in Fig. 113. Referring to Fig. 112, the values here 



500 



400 



300^ 
% 

20og 

!00 



1 1 1 1 1 1 


































P.SOKW UNIT 




































mn JCW 1 IMIT— 




































7S K W 1 IMIT J _, 










































































'MAX TOTAL KW^ 




~ 


















































































































































































































































rH 


— 


-- 


-■ 


•- 


- 


"1 


— , 


-H 




























































1 














































paVFR INIT.S IN KW 




































1 1 


1 












-- 


-- 
























^. 




.— 


.-, 




— 


... 


-- 


— 


— 












































































































































































— 


— 


-- 


— 


— 






























— 1 




_ 







)2 I 2 3 4 5 e "7 6 9 10 11 12 I 2 3 4 5 6 7 6 9 lO II 12 
AM M PM 

HOURS 

Fig. 112. 



given are assumed, for illustration, to be those recorded at 
the switchboard of the typical plant on a day when heavy 
service is required. The curves show that the 75 K. TF. unit 
runs from 12 P. M. to 7 A. M. and from 6 P. M. to 12 P. M. 
with an output of 25 K. TT. It also runs from 7 A. M. to 10 A. 



224 



HEATING AND VENTILATION 



M. and from 4 P. M. to 6 P. M. under full load. The 150 K. TV. 
unit runs from 4 A. M. to 7 A. M. with an output of 100 K. W. 
and then increases to 125 K. W. for the entire time until 6 P. M. 
when it is shut down. The 250 K. W. unit is started up at 7 
A. M. and runs until 6 P. M. under full load, when the load 
drops off to 150 K. TT, and continues until 10 P. M. when the 
unit is shut down, leaving- only the 75 K. W. unit running-. The 
heavy solid line shows all the power curves superimposed 
one upon the other. Having given the K. TF. output, the gen- 
eral formula for determining the horse-power of the engines 
is 

K. TT. X 1000 
I. II. P. = (66) 

where E and E' are the efficiencies of the generator and en- 
gine respectively. If we assume the efficiency of the g-ener- 
ator to be 90 per cent., and that of the engine to be 92 per 
cent., then formula 66 becomes 



I. n. p. = 



K. TT. X 1000 
746 X .90 X .92 



= approx. 1.62 K. TT. (67) 



Assuming that the 250 K. TT. unit consumes 24 pounds, the 
150 K. TF. unit 32 pounds, and the 75 K. TF. unit 32 pounds of 
steam per /. E. P. hour respectively, when running under 

























1 
























<^4 CX 
















?5 


QO 














P^l^o 














22 I 






























































































20 2 
















?(] 


Ofif 




; 








iap88 






























r*" 




IftR 


^0 
























-8^ 






























































































16 ^ 
14 ^ 






















i=;flnn 














































— 




















































































































12° 
































































,S] 


rtAM HDN.S 


JM^TION 


















I0§ 




















1 1 nr 








































pn\ 


fCR UNITS 






















8 g 








































m 


















lii^d 


























1 




iipft 
















648g1 






































6° 
























































4 « 


































































































?? 




1490 — 













































»- 




129(f) — 













































12 123456189 10 Jl 12 1234567 
AM M 

HOURS 
Fig. 113. 



9 10 II 12 
PM 



DISTRICT HEATING 225 

normal loads, we have the total steam consumed in the three 
units at any time shown by the lower curve in Fig*. 113. 
The upper curve shows the 15 per cent, added allowance for 
smaller units not included in the above list. The values 
assumed for efficiencies and the values for steam consump- 
tion are reasonable, and may be used if a more exact 
figure is not to be had. 

It will be seen that the maximum steam consumption in 
the generating- units in the power plant is 23100 pounds per 
hour and the minimum is 1490 pounds per hour. These two 
amounts, then, together with the exhaust steam from the 
circulating pumps on the heating system, if a hot water 
system is installed, and that from the pumps in the city 
water supply, w^ill determine the capacity of the exhaust 
steam heaters on the hot water supply and the capacity of 
the boilers or economizers to be used as heaters when the 
exhaust steam is deficient. 

142. Amount of Heat Available for Heating Purposes 
in Exhaust Steam, Compared w^ith That in Saturated Steam 
at the Pressure of the Exhaust: — To study the effect of ex- 
haust steam upon heating problems and to determine, if 
possible, the theoretical amount of heat given off with 
the exhaust steam under various conditions of use, let us 
make several applications: first, to a simple high speed 
non-condensing engine using saturated steam; second, to 
a compound Corliss non-condensing engine ussing saturated 
steam; third, to the first application when superheated 
steam is used instead of saturated steam; and fourth, to a 
horizontal reciprocating steam pump. Assume the follow- 
ing safe conditions. Case one — boiler pressure 100 pounds 
gage; pressure of steam entering cylinder 97 pounds gage; 
quality of steam at cylinder 98 per cent.; steam consump- 
tion 31 pounds per indicated horse-ipower hour; one per 
cent, loss in radiation from cylinder; and exhaust pressure 
2 pounds gage. Case two — boiler pressure 125 pounds gage; 
pressure at high pressure cylinder 122 pounds gage; quality 
of steam entering high pressure cylinder 98 per cent.; 
steam consumption 22 pounds per indicated horse-power 
hour; 2 per cent, loss in radiation from cylinders and re- 
ceiver pipe, and exhaust pressure 2 pounds gage. Case 
three — same as case one with superheated steam at 150 de- 
grees of superheat. Case four — as stated later. 



226 HEATING AND VENTILATION 

The number of B. t. u. exhausted with the steam, in 
any case, is the total heat in the steam at admission, minus 
the heat radiated from the cylinder, minus the heat ab- 
sorbed in actual work in the cylinder. 

High speed engine. Case one. — Let r = -heat of vaporiza- 
tion per pound of steam at the stated pressure, x — quality 
of the steam at cut-off, q = heat of the liquid in the 
steam per pound of steam, and Ws — pounds of steam per 
indicated horse-power hour. From this the total number 
of B. t. u. entering the cylinder per horse-power hour is 

Total B. t u. = Ws (xr + q) (68) 

From Peabody's steam tables r = 881, x — .98 and q = 307; 
then if Ws = 34, initial B. t. u. = 34 (.98 X 881 + 307) = 
39792.92. Deducting the heat radiated from the cylinder 
we have 39792.92 X .99 = 39395 B. t. u. per horse-power 
left to do work. The B. t. u. absorbed in mechanical work 
(useful work -j- friction) in the cylinder per horse-power 
hour is (33000 X 60) -- 778 = 2545 B. t. u. Subtracting 
this work loss we have 39395 — 2545 = 36850 B. t. u. given 
up to the exhaust per horse-power hour. Comparing this 
value with the total heat in the same weight of saturated 
steam ^at 2 pounds gage, we have 100 X 36850 -^ (34 X 
1152.8) — 94 per cent. 

Compound Corliss engine. Case two.— With the same terms 
as above let r = 867.4, x = .98, q = 324.4, and Ws = 22, 
then the initial B. t. u. = 22 (.98 X 867.4 + 324.4) = 25837.9. 
Less 2 per cent, radiation loss = 25837.9 X .98 == 25321.14 
B. t. u. The loss absorbed in doing mechanical work in the 
cylinder per horse-.power is, as before, 2545 B. t. u. Sub- 
tracting this we have 25321.14 — 2545 = 22776.14 B. t. u. 
given up to the exhaust per horse-power hour. Comparing 
as before with saturated steam at 2 pounds gage, we have 
100 X 22776.14 -^ (22 X 1152.8) = 90 per cent. 

Case three. — Now suppose superheated steam be used in 
the first application, all other conditions being the same, 
the steam having 150 degrees of superheat, what difference 
will this make in the result? The total heat entering the 
cylinder now is the total heat of the saturated steam at 
the initial pressure plus the heat given to it in the super- 
heater. Let Cp = specific heat of superheated steam and 



DISTRICT HEATING 227 

td = the degrees of superheat, then the total heat of the 
superheated steam is 

Total B. t. u. (sup.) = Ws (xr -{- q -\- Cpta) (69) 

This for one horse-power of steam (34 pounds), if the 
specific heat of superheated steam is .54, will be 34 X .99 
X (1188 + .54 X 150) = 42714.5 B. t. u. and the heat turned 
into the exhaust will be 42714.5 — 2545 = 40169.5 B. t. u. 
Comparing- this with the heat in saturated steam at 2 
pounds gage, we have 100 X 40169.5 -^ (34 X 1152.8) = 102 
per cent. 

Case four. — Pump exhausts are sometimes led into the 
Bupply and used for heating purposes along with the engine 
exhausts. If such conditions be found, what is the heating 
value of such steam? Assume the live steam to enter the 
steam cylinder of the pump under the same pressure and 
quality as recorded for the high speed engine. The steam 
is cut off at about % of the stroke and expands to the end 
of the stroke. With this small expansion the absolute 
pressure at the end of the stroke will be approximately 
% X 112 = 98 pounds, and if enough heat is absorbed from 
the cylinder wall to bring the steam up to saturation at 
the release pressure, we ^AU have a total heat above 32 
degrees, in the exhaust steam per pound of steam at 98 
pounds absolute, of 1185.6 B. 't. u. Comparing this with a 
pound of saturated steam at 2 pounds gage, we have 
100 X 1185.6 ^ 1152.8 = 103 per cent. Under the con- 
ditions such as here stated with a high release pressure, 
a small expansion of steam in the cylinder and dry steam 
at the end of the stroke, it is possible to suddenly drop the 
pressure from pump release to a low pressure, say 2 pounds 
gage, and have all the steam brought to a state approach- 
ing superheat. It is not likely, however, that the steam 
is dry at the end of the stroke in any pump exhaust, be- 
cause the heat lost in radiation and in doing work in the 
slow moving pump would be such as to have a considerable 
amount of entrained water with the steam, thus lowering 
the quality of the steam. These above conditions are ex- 
treme and are not obtained in practice. 

From cases one and two it would appear that the 
greatest amount of heat that can be expected from engine 
exhausts, for use in heating systemis at or near the pres- 
sure of the atmosphere, is 90 to 94 per cent, of that of 



HEATING AND VENTILATION 



saturated steam at the same pressure. The percentage will, 
in most cases, drop much below this value. All things con- 
sidered, exhaust stea7n haring SO to 85 prr cent, of the value of 
saturated steam at the same pressure is jyrobahly the safest rating tchen 
calculating the amount of radiation ichich can le supplied hy the 
engines. In many cases no doubt this could be exceeded, but 
it is always best to take a safe value. On the other hand, 
Khen figuring the amount of condenser tube surface or rcheater tube 
surface to condense the steam, it would be best to take exhaust steam 
at 100 per cent, quality, since this would be working toward 
the side of safety. 

In plants where the exhaust steam is used for heating 
purpo.ses and where the amount supplied by direct acting 
steam pumps is large compared with that supplied by the 
power units, it is possible to have the quality of the ex- 
hausts anywhere between 800 and 1000 B. t. u. per pound 
of exhaust. It should be understood that saturated steam 
at any stated pressure always has the (same number of 
B. t. u. in it, no matter whether it is taken directly from 
the boiler, or from the engine exhaust. A pound of the 
mixture of steam and entrained water, taken from engine 
exhausts, should not be considered as a pound of steam. 
If we are speaking of a pound of exhaust steam without 
the entrained water as compared with a pound of saturated 
steam at the same pressure, they .are the same, but a pound 
of engine exhaust or mixture is a different thing. ^^^^ 




n 
u 

j 


iV?r 



& 



D 



m 



h^ri^ ru= 



iF=rr 



p 



:zr 



a 






Fig. 114, 



DISTRICT HEATING 



229 



HOT WATER SYSTEMS. 

143. Four General Classifications of hot water heating- 
may be found in current work, two applying to the conduit 
piping- system and two to the power plant piping system. 
The first, known as the one-pipe complete circuit system, is shown 
in Fig. 114. It will be noticed that the water leaves the 
power plant and makes a complete circuit of the district, 
as A, B, C, D, E, F, G, through a single pipe of uniform 
diameter. From this main are taken branch mains and 
leads to the various houses, as a, 'b, c and d, e, each one 
returning to the principal main after having made its own 
minor circuit. The second is known as the two-pipe high 
pressure system, in which two main pipes of like diameter 
laid side by side in the same conduit, radiate from the 
power plant to the farthest point on the line reducing 
in size at certain points to suit the capacity of that part 
of the district served. This system is represented by Fig. 
115. In the one-pipe system the circulation in the various 
residences is maintained, in part, by what is known as the 
shunt system, and in part, by the natural gravity circula- 
tion. The circulation in the two-pipe system is main- 
tained by a high differential pressure between the main 
and the return at the same point of the conduit. The force 
producing movement of the water in the shunt system is, 
therefore, very much less than in the two-pipe system. As a 
consequence, the one-pipe system has a lower velocity of the 

ii 



n 

u 


j 


r- 




Rower Hou&t 



115. 



230 HEATING AND VENTILATION 

water in the houses and larger service pipes than the two- 
pipe system. 

In many cases it is desired to connect central heating 
mains to the low pressure hot water systems in private 
plants. Such connections may easily be made with either 
one of the two systems by installing some minor pieces 
of apparatus for controlling the supply. 

The third and fourth classifications, the open and closed 
system^s, have about the same meaning as when applied to 
gravity work in isolated plants. The first is open to the 
atmosphere at some point along the circulating system, usu- 
ally at the expansion tank which is placed on the return 
line just before the circulating pumps. The closed system 
presupposes some form of regulation for controlling exces- 
sive or deficient pressures without the aid of an expansion 
tank. In such ca&es pumps with automatic control may be 
used for taking care of the reserve supply of water. In the 
open system the exhaust steam may be injected directly into 
the return circulating water by the use of an open heater 
or a com-mingler. The open heater and com-mingler cannot 
be used on the pressure side of the pumps. Surface con- 
densers or reheaters, heating boilers and economizers may 
be used on either open or closed systems. 

144. Amount of W ater Needed per Hour as a Heating 
Medium:— All calculations must necessarily begin with the 
heat lost at the residence. Referring to the standard room 
mentioned in Art. 80, we find the heat loss to be 14000 B. t. u. 
per hour, requiring 84 square feet of hot water heating sur- 
face to heat the room. Let the circulating water have the 
following temperatures: leaving the power plant 180°, enter- 
ing the radiator 177°, leaving the radiator 157°, and entering 
the power plant 155°. According to these figures, which may 
be considered fair average values, the water gives off to the 
radiator 20 B. t. u. per pound or 166.6 B. t. u. per gallon, thus 
requiring 14000 - 166.6 = 84 gallons of water per hour to 
maintain the room at a temperature of 70°. From this a 
safe estimate may be given for design, i. e., each square foot of 
not water radiation in tUe city will require approximately one gallon 
of water per hour, which in a plant operating under high effi- 
ciency may be reduced to 6 pounds per square foot per hour. 
It is very certain that some plants are designed to supply 
less than one gallon, but in such cases it ^'^-''f'^:^^^^^^ 
temperature of the circulating water and allows Uttle chance 



DISTRICT HEATING 231 

for future expansion of the plant. A drop of 20 degrees, 
i. e., 20 B. t. u. heat loss per pound of water passing- through 
the radiator, is probably the most satisfactory basis. All 
things considered, the above italicised statement will satisfy 
every condition. (See Art. 173). Having the total number 
of square feet of radiation in the district, the total amount 
of water circulated through the mains per hour can be 
obtained, after which the size of the pumps in the power 
plant may be estimated. 

145. Radiation in the District: — The amount of radia- 
tion that may be installed in the district is problematical. In 
an average residence or business district the following fig- 
ures may easily be realized: tusiness square, 9000 square feet; 
residence square, J^oOO square feet. In certain locations these fig- 
ures may be exceeded and in others they may be reduced. 
Where the needs of the district are thoroughly understood a 
miore careful estimate can easily be made. It is always well 
to make the first estimate a safe one and any possible in- 
crease above this figure could be taken care of as in Art. 
144. Referring to Fig. Ill, an estimate of the amount of 
radiation that may be expected in this typical case, if we 
assume ten business squares and twenty-one residence 
squares, is 184500 square feet. This will call for the circu- 
lation of 184500 gallons of water per hour. 

146. Future Increase in Radiation: — From the tempera- 
tures given in Art. 144, it will be seen that each pound of 
water takes on 25 B. t. u. at the power plant and that there 
is a possible increase of 212 — 180 = 32 B. t. u. per pound that 
may be given to it, thus increasing the capacity of the system 
approximately 125 per cent. It would not be safe to count 
on such an increase in the average plant because of a defec- 
tive layout in the piping system or because of a low effi- 
ciency in some of the pumps or other apparatus in the 
plant. If, however, a plant is installed according to the 
above figures, the capacity may be quite materially increased 
by increasing the temperature of the outgoing water at th« 
plant to 212\ 

147. The Pressure of the AVater in the Mains! — The ele- 
vation above the plant at which a central station can supply 
radiation is limited. Water at 180° will weigh 60.55 pounds 
per cubic foot, and the pressure caused by an elevation of 1 
foot is .42 pound per square inch. From this the static pres- 



232 HEATING AND VENTILATION 

sure at the power plant, due to a hydraulic head of 100 feet, 
is 42 pounds per square inch. This value should not be ex- 
ceeded, and generally, because of the influence it has on the 
machines and pipes toward producing leaks or complete 
ruptures, a less head than this is desirable. A static pres- 
sure of 42 pounds may be expected to produce, in a well de- 
signed plant, an outflow pressure of 65 to 75 pounds per 
square inch and a return pressure of 15 to 20 pounds per 
square inch, when working under fairly he.avy service. In 
any case where the mains are too small to supply the radia- 
tion in the system properly, we may expect the value given 
for the outflow to increase and that for the return to de- 
crease. A safe set of conditions to follow is: head, in feet, 
60; static pressure, in pounds per square inch, 25; outgoing 
pressure at the pumps, in pounds per square inch, 50; return 
pressure at the pumps, in pounds per square inch, 5. 
This differential pressure of 45 pounds is caused by the 
friction losses in the piping system, pumps and heaters. 
Long pipe systems, as these are called, have much greater 
friction losses in the long runs of piping than in the ells, 
tees, valves, etc., hence, the friction head of the pipes is all 
that is usually considered. Where the minor losses are 
thought to be large, they may be accounted for by adding 
to the pipe loss a certain percentage of itself, say 10 to 20 
per cent. Pump power is figured from the differential pressure. 

The maximum and minimum pressures in the system are 
due to two causes; first, the static head, and second, the 
frictional resistances. These extremes of pressure are ap- 
proximately— s^otic head plus (or minus) one-half the frictional 
resistances. To obtain the frictional resistances, Chezy's for- 
mula, 70, is recommended. See Merriman's **A Treatise 
on Hydraulics," Arts. 86 and 100, and Church's "Mechanics 
of Engineering," Art. 519. 

7i/=— -X— (70) 

d 2g 

where ht = feet of head lost in friction, = friction factor 

(synonymous with coefficient of friction. For clean cast 

iron pipes with a velocity of 5 to 6 feet per second this 

has been found to vary from .0065 to .0048 for diameters 

between 3 and 15 inches respectively. .005 is suggested as 

a safe average value to use), I — length of pipe in feet, 

V = velocity of water in feet per second, d = diameter 

of pipe in feet and 2g = 64.4. 



DISTRICT HEATING 233 

Applicatiox. — In Fig*. 115, let it be desired to find the 
differential pressure at the pumps due to the friction losses 
in the line A, B, C, D, E. The lengths of the various parts 
are: power plant to A, 200 feet; A to B, 500 feet; B to 0, 
1500 feet; G to D, 1500 feet; and D to E, 500 feet. Assume, 
for illustration, that the total radiation in square feet 
beyond each of these points is: power plant, 125000; A, 85000; 
B, 50000; 0, 28000; and D, 12000. This requires 125000, 85000, 
50000, 28000 and 12000 gallons of water per hour, or 4.74, 
3.27, 1.75, 1 and .44 cubic feet of water per second, respec- 
tively, passing these points. Now, if the velocities be 
roughly taken at 6 and 5 feet per second, (pipes near the 
power plant may be given somewhat higher velocities than 
those at some distance from the plant), the pipes will be 12, 
10, 8, 6 and 4 inches diameter. In applying the formula to 
one part of the line we show the method employed for each. 
Take that part from the power plant to A, With v = 6 

4 X .005 X 200 X 36 

hf = = 2.2 feet. 

64.4 X 1 

It should be noted here that formula 70 refers to pipes 
where all the ivater that enters at one end passes out the other. 
This is not true in heating- mains where a part of the water 
is drawn off at intermediate points. On the other hand, 
Merriman, Art. 99, explaiins that a water service main, where 
the water is all taken off from intermediate tappings and where 
the velocity at the far end is zero, causes only one-third of the 
friction given by the above formula. The case under consid- 
eration falls somewhere between these two extremes, the part 
next the power plant approaching the former and the last 
part of the line exactly meeting the conditions of the latter. 
Assuming the mean of 'these two conditions, which is 
probably very close to the actual, gives two-thirds of 'that 
found by the formula. Now since this is a double main 
system, i. e., main and return of the same size, the friction 
head for the two lines becomes 2.94 feet, from the power 
plant to A. In a similar way the other parts may be tried 
and the results from the entire line assembled in convenient 
form as in Table XXVII. 



234 



HEATING AND VENTILATION 



TABLE XXYIL 



Distance between points 

Radiation supplied 

Volume of water passing 

point in cu. ft. per sec 

Velocity f. p. s 

Area of pipe sq. ft 

Diam. of pipe in ft 

lif by (73) for flow main 

Jif (taking % value) 

Tif (% val. flow and return).... 



P. p. 

to A. 


AtoB 


Bto C 


CtoD 


200 


500 


1500 


1500 


125000 


85000 


50000 


28000 


4.74 


3.27 


1.75 


1. 


6 


6 


5 





.79 


.545 


.35 


.20 


1 


.83 


.66 


.5 


2.2 


6.7 


17.4 


23.3 


1.47 


4.47 


11.6 


15.5 


2.94 


8.94 


23.2 


31.0 



DtoE 



500 
12000 



.44 



.087 



11.7 

7.8 

15.6 



From the last line of the table we obtain the total 
friction head for both mains, not including ells, tees, valves, 
etc., to be 81.6 feet. This is equivalent to 34.3 pounds per 
square dnch. Now if we allow about 20 per cent, of all the 
line losses to cover the minor losses we have approximately 
40 pounds differential pressure, which is a reasonable value. 

148. Velocity of the W ater in the Mains and the Dia- 
meter of the Plains: — The district is first chosen and the 
layout of the conduit system is made. This is done inde- 
pendently of the sizes of the pipes. When this layout is 
finally completed, the pipe sizes are roughly calculated for 
all the important points in the system and are tabulated 
in connection with the friction losses for these parts, as 
in Art. 147. When this is done, formula 71, which is rec- 
ommended to be used in connection v/ith formula 70, may be 
applied and the theoretical diameters found. (The approxi- 
mate diameters and the friction heads need not be calcu- 
lated in formula 70 for use in formula 71, providing some 
estimate may be made for the value of hr, for the various 
lengths of pipe. If desired, hf may be assumed without any 
reference to the diameter, but this is a rather tedious pro- 
cess. For good discussion of this point see Church's Hy- 
draulic Motors, Arts. 121-124 b.) 



.629 



[ 



X 



(i>lQ~ IVo 



hf 



] 



(71) 



where d, hf, and 7 are the same as in formula 70, and Q = 
cubic feet of water passing through the pipe per second. 
This formula "differs from those given in the references 
stated, in that the term % is inserted as a mean value be- 



DISTRICT HEATINa 235 

tween the two extreme conditions, as stated in Art. 147. 
ApplicatioxX. — Let it be desired to find the diameter for the 
single main between the power plant and A, Art. 147, with 
hf =^ 1.47 

[2 X.005 X 200 X (4.74)2 y/^ 
• I = 1 ft. == 12 in. 
3 X 1.47 -* 

Applying- to the entire line with hf as given in next to last 
line of Table XXVII, gives power plant to A, d = 12 inches; 
A to B, d = 10 inches; B to C, d z= S Inches; to Z>, ^ = 6 
inches; and Z> to -&, fZ = 4 inches. 

In some cases, when close estimating is not required, 
it is satisfactory to assume a velocity of the water and find 
the diameter without considering the friction loss. In many 
cases, however, this would soon prove a positive loss to the 
company. With a low velocity, the first cost would be large 
and the operating cost would be low. On the other hand, 
if the velocity were high, the first cost would be small and 
the operating cost and depreciation would be large. As an 
illustration of how the friction head increases in a pipe of 
this kind with increased velocity, refer to the run of mains 
between B and C. Assuming a velocity of 10 feet per 
second, which in this case would be very high, the friction 
head, hf, for the single main, becomes 62 and the theoretical 
diameter is 5.5, say 6 inches. The friction head, as will be 
seen, is 5.4 times the corresponding value when the velocity 
was 5 feet per second. Since the pump must work contin- 
ually against this head, it would incur a financial loss that 
would soon exceed the extra cost of installing larger pipes. 
It is found in plants that are in first class operation that 
the velocities range from 5 to 7 feet per second. 

The calculations in Arts. 147 and 148 are very much 
simplified by the use of the chart shown in the Appendix. 
In planning a system of this kind, find the friction head 
on the pumps and the diameters of the pipes for various 
velocities, say 4, 6, 8 and 10 -feet per second. Estimate the 
probable first cost and the depreciation of the conduit sys- 
tem for each velocity, and balance these figures with the 
operating cost for a period of, say five years, to see which is 
the most economical velocity to use in figuring the system. 

149. Service Connectioiis are usually installed from 30 
to 36 inches below the surface of the ground, and are in- 
sulated in some form of box conduit which compares favor- 



236 HEATING AND VENTILATION 

ably with that of the main conduit. Service branches are 
IV4., 1% and 2 inch wrought iron pipe. These are usually 
carried to the building from the conduit at the expense of 
the consumer. Such branch conduits are not drained by 
tile drains. See Art. 176. 

150. Total Steam Available and B. t. u. Liberated per 
Hour for Heating tlie Circulating Water:— The amount of 
steam available for heating the circulating water is that 
given off by the generating units, plus that from the cir- 
culating pumps, plus that from the city water supply pumps 
if there be any, plus that from the auxiliary steam units 
in the plant, i. e., small pumps, engines, etc. In the typical 
application this amounts to 23100 + 12720 + 8680 = 44500 
pounds per hour. 

This steam, of course, is not equal to good dry steam in 
heating value because of the work it has done in the engine 
and pump cylinders, but a good estimate of its value may 
be approximated. In addition to the terms used in for- 
mula 68, let q' = heat in the returning condensation per 
pound; then the heat available for heating purposes per 
pound of exhaust steam is 

B. t. u. = 3pr + q — a' C^S) 

It is probably safe to consider the quality of the steam as 
85 per cent, of that of good dry steam at the same pressure. 
Since the pressure of the exhaust from a non-condensing 
engine, as it enters the heater, is near that of the atmos- 
phere, and since the returning condensation is at a tempera- 
ture of about 180°, the total amount of heat given off from 
a pound of exhaust steam to the circulating water is 
B. t. u. = .85 X 969.7 + 180.3 — (180.3 — 32) = 856, say 850. 
If Ws be the pounds of exhaust steam available, the total 
number of B. t. u. given off from the exhaust steam per hour is 
Total B. t u. = 850 Ws (73) 

Applying this to the typical power plant gives 850 X 
44500 = 37825000 B. t. u. per hour. This amount is probably 
a maximum under the conditions of lighting units as stated, 
and would be true for only 5 hours out of 24. At other 
times the exhaust steam drops off from the lighting units 
and this deficiency must be made good by heating the circu- 
lating water directly from the coal, by passing the water 
through heating boilers or by passing it through economiz- 



DISTRICT HEATING 237 

ers where it is heated by the waste heat from the stack 
gases. 

151. Amount of Hot AVater Radiation in the District 
that can be Supplied by One Pound of Kxhaust Steam on a 
Zero Day: — In Art. 144, each pound of water takes on 25 
B. t. u. in passing through the reheaters at the power plant, 
and gives off at least 20 B. t. u. in passing through the 
radiator. The number of pounds of water heated per pound 
of steam per hour is, Ww = (Total B. t. u. available per 
pound of exhaust steam per hour) ~ 25, and the total radia- 
tion that can be supplied is 

Total B. t u. available per lb. of exhaust steam per hr. 

R,o = (74) 

8.33 X 25 

which for average practice reduces to 

850 
Rw = = 4 square feet approx. (75) 

208 

Applj^ing formula 74 for the five hour period when the 
exhaust steam is maximum gives Rw = 37825000 -f- 208 = 
181851 square feet. It is not safe to figure on the peak load 
conditions. It is better to assume that for half the time, 
35000 pounds of steam are available and will heat 35000 
X 4 — 140000 square feet of radiation. 

152. The Amount of Circulating Water Passed through 
the Heater Necessary to Condense One Pound of Kxhaust 
Steam is 

Total B. t. u. available per lb. of exhaust steam per hr. 

Ww — (76) 

25 

With the value given above for the exhaust steam this 
becomes, for 100 and 85 per cent, respectively, 

1000 

yVvj = = 40 pounds (77) 

25 

850 

Ww — — 34 pounds (78) 

25 

153. Amount of Hot AVnter Radiation in the District 
that can be Heated by One Horse-Po^er of Exhaust Steaui 
from a Non-Condensing Kngine on a Zero Day:— 

Rw = i X (pounds of steam per H. P. hour) (79) 



23S HEATING AND VENTILATION 

This reduces for the various types of engines, as follows: 

Simple high speed 4 X 34 = 136 square feet. 

medium " 4 X 30 = 120 

Corliss 4 X 26 = 104 

Compound high " 4 X 26 = 104 

" medium" 4 X 25 = 100 

" Corliss 4 X 22 = 88 

154. Amount of Radiation that can be Supplied by Ex- 
haust Steam in Formulas 74 and 75 at any other Temper- 
ature of the AVater, tw, than that Stated, witli the Room 
Temperature, f, Remaining the Same: — The amount of heat 
passing through one square foot of the radiatoT to the room 
is in proportion to tio — /'. In formulas 74 and 75, tw — f = 
100. Now if tw be increased co degrees, so that tw — V = 
(100 + x) then each square foot of radiation in the building 

100 -f a? , ^ ^ 

will give off times more heat than before and 

100 

each pound of exhaust steam Tvill supply only 

4 X 100 ^.^. 

Rw = ■ square feet CoO; 

100 + CO 

This for an increase of 30 degrees, which is probably a max- 
imum, is 

4 

Rw rr . =z 3 square feet (81) 

1.3 

Compared with formula 75, formula 80 shows, with a hi^ii 
temperature of the water entering the radiator, that less 
radiation is necessary to heat any one room and that each 
square foot of surface becomes more nearly the value of an 
equal amount of steam heating surface. Calculations for 
radiation, however, are seldom made from high tempera- 
tures of the water, and this article should be considered an 
exceptional case. 

155. Exhaust Steam Condenser (Reheater), for Reheat- 
ing the Circulating Water: — In the layout of any plant 
the reheaters should be located close to the circulating 
pumps on the high pressure side. They are usually of 
the surface condenser type. Fig. 116, and may or may not be 
installed in duplicate. Of the two types shown in the fig- 
ure, the water tube type is probably the more common. The 
same principles hold for each in design. In ordinary heaters 
for feed water service, wrought iron tubes of IV2 to 2 inches 



DISTRICT HEATING 



239 



ST 



Ir 



WATER 

m 



\ I ^ 



STLAM DRIP 



WATLR-TUBL TYPE 



^. 



Fisr. 116. 



WATER 






^ 



VVATLR 5TLAM 
DRIP 

STLAM-TUBE TYPE 



diameter are generally used, but for condenser work and 
where a rapid heat transmission is desired, brass or copper 
tubes are used, having diameters of % to 1 inch. In heating- 
the circulating water for district service, the reheater is 
doing very much the same work as if used on the condens- 
ing system for engines or turbines. The chief difference is 
in the pressures carried on the steam side, the reheater con- 
densing tlie steam near atmospheric pressure and the con- 
denser carrying about .9 of a perfect vacuum. In either case 
it should be piped on the water side for water inlet and out- 
let, while the steam side should be connected to the exhaust 
line from the engines and pumps, and should have proper 
drip connection to draw the water of condensation off to a 
condenser pump. This condenser pump usually delivers the 
water of condensation to a storage tank for use as boiler 
feed, or for use in making up the supply in the heating sys- 
tem. 

In determining the details of the condenser the following 
important points should be investigated: the amount of 
heating surface in the tubes, the size of the water inlet and 
outlet, the size of the pipe for the steam connection, the size 
of the pipe for the water of condensation and the length 
and cross section of the heater. 

156. Amount of Heating Surface in the Reheater Tuhesj 
— The general formula for calculating the heating surface in 
the tubes of a reheater (assuming all heating surface on 
tubes only), is 

Total B. t. u. given up bv the exhaust steam per hr. 

Rt = • (82) 

K (Temp. diff. between inside and outside of tubes) 

The maximum heat given off from one pound of exhaust 
steam in condensing at atmospheric pressure is 1000 B. t. u., 
the average temperature difference is approximately 47 
degrees, and K may be taken 427 B. t. u. per degree dif- 



240 HEATING AND VENTILATION 

ference per hour. In determining K, it is not an easy mat- 
ter to obtain a value that will be true for average practice. 
Carpenter's H. & V. B. Art. 47 quotes the above figure for 
tests upon clean tubes, and volumes of • water less than 
1000 pounds per square foot of heating surface per hour. 
It is found, however, that the average heater or condenser 
tube with its lime and mud deposit will reduce the efficiency 
as low as 40 to 50 per cent, of the maximum transmission. 
Assume this value to be 45 per cent.; then if Ws is the 
number of pounds available exhaust steam, formula 82 
becomes 

1000 Ws 1000 Ws 1000 Ws TF« 

Rt — — : == = (83) 

K{ts—tw) 427X.45X47 9031 9.1 

In "Steam Engine Design," by Whitham, page 283, the 
following formula is given for surface condensers used on 
shipboard: 

W L 

S = 

cK (Ti — t) 

where S = tube surface, W = total pounds of exhaust steam 
to be condensed per hour, L — latent heat of saturated steam 
at a temperature Ti, K = theoretical transmission of B. t. u. 
per hour through one square foot of surface per degree dif- 
ference of temperature = 556.8 for brass, c = efficiency of 
the condensing surface = .323 (quoted from Isherwood), Tx =■ 
temperature of saturated steam in the condensers, and t — 
average temperature of the circulating water. 

With L = 969.7, c = .323, K = 556.8 and Tx — t = 47, we 
may state the formula in terms of our text as 

969.7 Ws 969.7 Ws Ws 

Rt = = — (84) 

.323X556.8X47 8446 8.7 

In Sutcliffe "Steam Power and Mill Work," page 512, the 
author states that condenser tubes in good condition and set 
in the ordinary way have a condensing power equivalent to 
13000 B. t. u. per square foot per hour, when the condensing 
water is supplied at 60 degrees and rises to 95 degrees at dis- 
charge, although the author gives his opinion that a trans- 
onission of 10000 B. t. u. per square foot per hour is all that 
should be expected. This checks closely with formula 83, 
which gives the rate of transmission 9031 B. t. u. per square 
foot per hour. 



DISTRICT HEATING 241 

The following empirical formula for the amount of heat- 
ing surface in a heater is sometimes used: 

Rt = .0944 Ws (85) 

where the terms are the same as before. 

Applicatiox. — Let the total amount of exhaust steam avail- 
able for heating the circulating water be 35000 pounds per 
hour, the pressure of the steam in the condenser be atmos- 
pheric and the water of condensation be returned at 180°; 
also, let the circulating water enter at 155° and be heated to 
180°. These values are good average conditions. The as- 
sumption that the pressure within the condenser is atmos- 
pheric might not be fulfilled in every case, but can be ap- 
proached very closely. From these assumptions find the 
square feet of surface in the tubes. 

35000 



Formula 


83, 


Rt 


— 


9.1 


— 


3846 


sq. 


ft. 






Formula 


84, 


Rt 


= 


35000 


= 


4023 


sq. 


ft. 






8.7 




Formula 


85, 


Rt 


= 


35000 


X 


.0944 


z= 


3304 s 


q. 


ft. 


Sutcliffe 




Rt 





1000 X35 


000 


- 3c 


00 sq. 


ft. 





10000 

If 3846 square feet be the accepted value it will call for 
three heaters having 1282 square feet of tube surface each. 

157. Amount of Reheater Tube Surface per Eng^ine 
Horse-Power: — Let ws be the pounds of steam used per 
/. H, P. of the engine; then from formula 83 

Ws 

Rt (per 7. H. P.) = (86) 

9.1 

This reduces for the various types of engines as follows: 

Simple high speed 34 -r- 9.1 = 3.74 square feet 

" medium " 30 -r- 9.1 = 3.30 

** Corliss 26 ^ 9.1 = 2.86 

Compound high ** 26 -r- 9.1 = 2.86 

" medium " 25 -f- 9.1 = 2.75 

" Corliss 22 -r- 9.1 = 2.42 

158. Amount of Hot IVater Radiation in the District 
that can be Supplied by One Square Foot of Reheater Tube 
Surface: — If the transmission through one square foot of 
tube surface be K {ts — tw) = 9031 B. t. u. per hour and the 



242 HEATING AND VENTILATION 

amount of heat needed per square foot of radiation per 
hour = 8.33 X 25 == 208, as given in formula 74, then 

9031 
Rw (per sq. ft. of tube surface) = — 43.4 sq. ft. (87) 

208 

159. Some Important Reheater Details: — Inlet and outlet 

pipes. — Having- three heaters in the plant, it seems rea- 
sonable that each heater should be prepared for at least one- 
third of the water credited to the exhaust steam. From 
Art. 151 this is 140000 -^ 3 = 46667 gallons — 10800000 cubic 
inches per hour. The velocity of the water entering and 
leaving the heater may vary a great deal, but good values 
for calculations may be taken between 5 and 7 feet per 
second. Assuming the first value given, we have the area 
of the pipe = 10800000 ^ (5 X 12 X 3600) = 50 square inches, 
and the diameter 8 inches. 

The size of the reheater shell. — Concerning the velocity 
of the water in the reheater itself, there may be differences 
of opinion; 100 feet per minute will be a good value to use 
unless this value makes the length of the tube too great for 
its diameter. If this is the case the tube will bend from 
expansion and from its own weight. At this velocity the 
free cross sectional area of the tubes, assuming the water 
to pass through the tubes as in Fig. 116, will be 150 square 
inches. If the tubes be taken % inch outside diameter, 
with a thickness of 17 B. W. G., and arranged as usual in 
such work, it will require about 475 tubes and a shell diam- 
eter of approximately 30 inches. If the inner surface of the 
tube be taken as a measurement of the heating surface and 
the total surface be 1282 square feet, the length of the re- 
heater tubes will be approximately 16 feet. 

The ratio of the length of the tube to the diameter is, 
iri this case, 256, about twice as much as the maximum ratio 
used by some manufacturers. It will be better, therefore, 
to increase the number of tubes and decrease the length. 
"U^ith a velocity of the water at 50 feet per minute, the 
values will be approximately as follows: free cross sec- 
tional area of the tubes, 300 square inches; number of tubes, 
950; diameter of shell, 40 inches; length of tubes, 8 feet. 
These values check fairly well and could be used. 

The size of exhaust steam connection. — To calculate this, use 
the formula 

144 Qb 
A^ (88) 



DISTRICT SEATIXC^ 243 

where Q* = volume of steam in cubic feet per minute, T = 
velocity in feet per minute, and A = area of pipe in square 
inches. "When applied to the reheater using 35000 pounds 
of steam per hour, at 26 cubic feet per pound and at a veloc- 
ity through the exhaust pipe of 6000 feet per minute, it gives 



= 360 sq. in = 22 in. d:a. 



60 X 6000 
Try also, from Carpenters H. & V. B., page 284 



d = V . 



1.2o (S9) 

Allowing 30 pounds of steam per H. P. hour for non-condens- 
ing engines we have 35000 -e- 30 = 1166 horse-power; then 
applying the above we obtain d = 16 inches. Comparing 
the two formulas, 88 and 89, the first Tvill probably admit of 
a more general application. The velocity 6000 for exhaust 
steam may be increased to 8000 for very large pipes and 
should be reduced to 4000 for small pipes. In the above 
applications a 20 inch pipe will suffice. 

The return pipe for condensation. — The diameter of the pipe 
leading to the condenser pump will naturally be taken from 
the catalog size of the pump installed. This pump would 
be selected from capacities as guaranteed by the respective 
manufacturers and should easily be capable of handling- the 
amount of water that is condensed per hour. 

T7i^ value of a high pressure steam connection. — If desired, 
z\^ : : . tL _iiay also be provided Tvith a high pressure 
s: ; : i-n, to be used ^vhen the exhaust steam is not 

s vr;. ; tI :. ~ .:s steam is then used through a pressure-re- 
ducing valve which admits the steam at pressures varying 
from atmospheric to 5 pounds gage. There is some question 
concerning the advisability of doing this. Some prefer to 
install a high pressure steam heater, as in Art, 160, to be 
used independently of the exhaust steam heaters. This 
removes all possibility of having excessive back pressure 
on the engine piston, as is sometimes the case where high 
pressure steam is admitted with the exhaust steam. 

It has been the experience of some who have operated 
such plants that where more heat is needed than can be 
supplied by the exhaust steam, it is better to resort to heat- 
ing boilers and economizers, than to use high pressure steam 
for heating. 



244 



HEATING AND VENTILATION 



160, High Pressure Steam Heater; — When this heater Is 
used i't is located above the boiler so that all the condensa- 
tion freely drains back to the boilers by gravity as in Fig. 
117. In calculating the tube surface, use formula 82 with 
the full value of the steam and the steam temperatures 
changed to suit the increased pressure. Such a heater as 
this gives good results. 




Fig. 117. 



161. Circulating Pumps: — Two types of pumps are In 
general use: centrifugal and reciprocating. Each type is 
somewhat limited in its operation. The centrifugal pump 
has difficulty in operating against high heads and the recip- 
rocating pump is very noisy when running at a high piston 
speed. Since each type is in successful operation in many 
plants, no comparisons will be made between them further 
than to say that the former, being operated by a steam en- 
gine, may be run more economically than the latter because 
of the possibilities of using the steam expansively. It will 



DISTRICT HEATING 245 

be noted, however, that this same steam is to be used in the 
exhaust steam heaters for warming- the circulating water 
and hence there would be little, if any, direct loss from this 
source in the use of the reciprocating pump. 

Having given the maximum amount of water to be 
circulated per hour, consult trade catalogs and select the 
number of pumps and the size of each pump to be installed. 
The sizes of the pumps can easily be determined when the 
number of them has been decided upon. This latter point 
is one upon which a difference of opinion will probably be 
found. No exact rule can be applied. In a plant of, say 
not more than 150000 square feet of radiation (150000 gal- 
lons of water per hour, or 3 million gallons for twenty-four 
hours), some designers would put in three pumps, each 
having 1.5 million gallons capacity; in which case one pump 
could be cut out for repairs and the other two would be 
able to care for the service temporarily. Other designers 
would use four pumps at about one million gallons each. 
The fewer the pumps installed, in any case, the greater 
should be the capacity of each. The following values will 
be found fairly satisfactory: 

1 Pump. Cap. = (1 to 1.25) times max. requirem't of system 

2 Pumps. " (each) = .75 

3 Pumps. " " = .5 

4 Pumps. ** ** = .3 

Having given the capacity of each pump in gallons of 
water per minute, the size, the horse-power and the steam 
consumption of each pump can be calculated. In obtaining 
the size of the pumip it will be necessary to know the speed, 
Y, of the piston in feet per minute, the sti'okes, N, per minute 
and the per cent, of slip, s (100 per cent. — S, where S = hy- 
draulic efficiency). The speed varies between 100, for small 
pumps, and 75, for large pumps. The strokes vary between 
200, for small pumps, and 40, for large pumps, and the slip 
varies between 5 and 40 per cent., depending upon the fit of 
the piston and the valves. In pumps that have been in serv- 
ice for some time the slip will probably average 20 per cent. 

The cross sectional area of the water cylinder in square 
inches is 

cubic inches pumped per minute 
W. C. A. — (90) 

>s X y X 12 



246 HEATING AND VENTILATION 

from which we may obtain the diameter of the water cyl- 
inder. 

The steam cylinder area is usually figured as a certain 
ratio to that of the water cylinder area, as 

S. C. A. = (1.5 to 2.5) X W. C. A. (91) 

from which we may obtain the diameter of the steam cylin- 
der. 

The length of the stroke, L, in inches, may be obtained 
from the speed and the number of strokes such that 

12 y 

L = (92) 

N 

All direct acting- steam pumps are designated by diam- 
eter of steam cylinder X diameter of water cylinder X length 
of stroke, as 

14'' X 12'' X 18" 

Duplex pumps have twice the capacity of single pumps 
having the same sized cylinders. 

To find the indicated horse-power, I. H. P., of the pumps, 
reduce the pressure head, p, in pounds per square inch, to 
pressure head in feet, h; multiply this by the pounds of 
water, W, pumped per minute and divide the product by 
23000 times the mechanical efficiency, E. 

W h 
I. H. P. = (93) 

33000 E 

To reduce from pressure head in pounds to pressure 
head in feet, divide the pressure head in pounds by weight 
of a column of water one square inch in area and one foot 
high. The general equation for this is 

144 p 
w 

where to = the weight of a cubic foot of water at the given 
temperature and p = differential pressure in pounds per 
square inch. 

In pump service of this kind the pressure head, p, 
against which the pump is acting, is not the result of the 
static head of water in the system but is due to the inertia 
of the water and to the resistance to the flow of water 



DISTRICT HEATING 247 

throug"h the piping system 'and the heaters. This frictional 
resistance may be calculated as shown in Art. 147. Read 
this part of the work over carefully. 

For an illustration of combined pressu-re head, p, and 
friction head, hf, see Art. 164 on boiler feed pumps. Having 
found the I. E. P. of any pump, multiply it by the steam con- 
sumption per /. H. P. hour and the result will be the steam 
consumption of the pump. This exhaust steam will be con- 
sidered a part of the general supply when figuring the size 
of the exha.ust steam heaters in the system. 

The m,echanical efficiency, E, of piston pumps depends 
upon the condition of the valves and upon the speed, and 
varies from 90 per cent, in new pumps, to 50 per cent, in 
pumips that are badly worn. A faiT average would be 70 
per cent. 

The steam consumption for reciprocating, simple and 
duplex non-condensing pumps would approximate 100 to 
200 pounds of steam per /. H. P. hour — the greater values re- 
ferring to the slower speeds. 

162. Centrifugal Pvimps: — Centrifugal pumps are of 
two classifications, the Volute and the Turbine. The prin- 
ciples upon which each operate are very similar. The ro- 
tating impeller, or rotor, with curved blades draws the 
water in at the center of the pump and delivers it from the 
circumference. The rotor is enclosed by a cast iron case- 
ment which is shaped more or less to fit the curvature of 
the edges of the blades on the rotor. Centrifugal pumps 
are used where large volumes of water are required at low 
heads. They are used in city water supply systems, in cen- 
tral station heating systems, in condenser iservice, in irri- 
gation work and in many other places where the pressure 
head operated against is not excessive. The efficiency of 
the average centrifugal pump is from 65 to 80 per cent., 
75 per cent, being not uncommon. In places where such 
pumps are used the head is usually below 75 feet, although 
some types, when direct connected to high speed motors, 
are capable of operating against heads of several hundred 
feet. 

(Some of the advantages of centrifugal pumps over hor- 
izontal ireciprocating pumps are: low first cost, simplicity, 
few moving parts, compactness, uniform flow and pressure 
of water, freedom from shock, possibilities of direct connec- 



248 HEATING AND VENTILATION 

tion to high speed motors and the ability to handle dirty 
water without injuring- the pump. 

One of the advantages of piston pumps over centrifugal 
pumps is the fact that they are more positive in their 
operation and work against higher heads. 

Centrifugal pumps, when connected to engine and tur- 
bine drives, benefit by the expansion of the steam and are 
much more economical than the direct acting piston pump, 
which takes steam at full pressure for nearly the entire 
stroke. The amount of steam used in the pumps in central 
station work, however, is not a serious factor, since all of 
the heat in the steam that is not used in propelling the 
water through the mains is used in -the heaters to increase 
the temperature of the water. 

The sphere of usefulness of the centrifug-al pump in 
central station heating is incre^asing. The direct acting 
piston pump, when operating at fairly high speeds, causes 
hammering and pounding in 'the transmission lines, and 
these noises are sometimes conveyed to the residences and 
become annoying to the 'occupants. This feature is not so 
noticeable in the operation of the centrifugal pump. 

Application. — In Art. 145 assume the capacity of the plant, 
10 business squares and 21 residence squares, to require 
184500 gallons of water per hour; the same to be pumped 
against a pressure head, Art. 147, of 50 — 5 pounds, by 
horizontal, direct acting piston pumps. Assume also the 
steam consumption of the pumps to be 100 pounds per /. H. P. 
hour and the average temperature of the water at the 
pumps to be (180 + 155) -h 2 = 167.5 degrees. Apply for- 
mula 93, where h = calculated total friction head for the 
longest line in the system (this is designated by lif in Art. 
147), or where p = total difference between the incoming 
and the outgoing pressures. With the weight of a cubic 
foot of water at 167.5 degrees = 60.87 pounds and with 
p =: 45, we have h = 106.5 feet, and the indicated horse-power 
of the pumps, assuming 65 per cent, mechanical efficiency, is 

184500 X 8.33 X 106.5 

/. H. P. = = 127.2 

33000 X.65 X 60 

From this the steam consumption will probably be 12720 
pounds per hour. 

If centrifugal pumps were selected, the horse-power 
would be calculated from the same formula, but the steam 



DISTRICT HEATING 24d 

consumption would probably be 30 to 40 pounds of steam 
per horse-power hour because of the expansive working of 
the steam. 

163. City W^ater Supply Pumps s — Horizontal, direct act- 
ing duplex pumps for use on city water supply service are 
the same as those used to circulate the water in heating" 
systems; hence, the foregoing descriptions apply here. The 
/. H. P. of the city water supply pumps would be calculated 
by use of formula 93. If the pumps lifted the water from 
the wells, as would probably be 'the case, the suction pres- 
sure would be negative and would be added to the force 
pressure. 

Application. — ^Assume the pressure in the fresh water 
mains 60 pounds and the suction pressure 10 pounds; 
therefore, p = 60 — ( — 10) = 70 pounds, and with the water 
at 65 degrees, li — 144 X 70 -^ 62.5 = 161 feet. These pumps 
are each rated at 1.5 million gallons in 24 hours, and deliver 
62500 X 8.33 = 520833 pounds of water per hour, when run- 
ning at full capacity. Assuming each pump to deliver 75 per 
cent, of the full requirement of the system, the total amount 
of water pumped per hour for the city water supply would 
approximate 520833 -f- .75 = 694444 pounds, and the total 
average horse-power used in pumping the water would be 

694444 X 161 

/. H. P. — = 86.8 

60 X 33000 X.65 

With 100 pounds of steam per horse-power hour, this would 
amount to 8680 pounds of steam available per hour for use 
in heating the circulating water. 

164. Boiler Feed Pumps: — Horizontal pumps for high 
pressure boiler feeding are selected in a similar way to the 
circulating pumps for the city water supply. Such units 
are called auxiliary steam units and, because the steam re- 
quired is small, they are sometimes piped to a feed water 
heater for heating the boiler feed. The velocity of the water 
through the suction pipe is about 200 feet per minute and 
in the delivery pipe about 300 feet per minute. The piston 
speed, the strokes per minute and the slip would be very 
much the same as stated under circulating pumps. Such 
pumps should have a pumping capacity about 'twice as great 
as the actual boiler requirements, and in small plants where 
only one pump is needed, the installation should be in 



250 HEATING AND VENTILATION 

duplicate. The sizes of the cylinders and the efficiencies are 
about as stated for the larger circulating pumps. 

In determining the horse-power of a boiler feed pump, 
four resistances must be overcome; i. e., pressure head, p, 
or boiler pressure; suction head, lis; delivery head, ha; and 
the friction head, hf. The first three values are usually 
given. The friction head includes the resistances in all pip- 
ing, ells and valves from the supply to the boiler. The fric- 
tion in the piping may be taken from Table 37, Appendix, or 
it may be worked out by formula 70. The friction in the ells 
and valves is more difficult to determine and is usually stated 
in equivalent length of straight pipe of the same diameter. 
A rough rule used by some in such cases is as follows: 
"to the length of the given pipe, add 60 times the nominal 
diameter of the pipe for each ell, and 90 times the diameter 
for each globe valve," then find the friction head as stated 
above. A straight flow gate or water valve could safely be 
taken as an ell. For simplicity of calculation, all of the 
above resistances may be reduced to an equivalent head, 
such that 

144 p 

he — h ^-d -\- hs + Tit (94) 

w 

where w = weight of one cubic foot of water at the suc- 
tion tempeirature, w may be obtained from Table 8, Ap- 
pendix, and hf may be taken from Table 37. The horse-power 
by formula 93 then becomes, if TF r= pounds of water pumped 
per minute, 

W X he 
I. H. P. = (95) 

33000^7 

Application. — Let p ^= 125 pounds gage, w = 62.5, ha = S 
feet, hs = 20 feet, horizontal run 'of pipe from supply to 
pump =: 20 feet, horizontal run of pipe from pump to boiler 
r= 30 feet; also, let the pump supply 89000 pounds of water 
per hour to the boiler. This is twice the capacity of the 
boiler plant. With this amount of water at the usual veloc- 
ity it will give a suction pipe of 4.5 inches diameter, and a 
flow pipe of 4 inches diameter. Let there be two ells and 
one gate valve on the suction pipe, and three ells, one globe 
valve and one check valve on the delivery pipe. We then 
have an equivalent of 107 feet of suction pipe, and 158 feet 
of delivery pipe. Referring to Table 37, hf is approxi- 
mately 7 feet, and the total head is 



DISTRICT HEATING 251 

144 X 125 

lie = h 8 + 20 + 7 =^ 323 feet. 

62.5 
y 

In most boiler feed pumps it is considered unnecessary 
to determine hf so carefully. A very satisfactory way is to 
obtain the ^total head pumped against, exclusive of the 
friction head, and add to at 5 to 15 per cent., depending 
upon the complications in the circuit. Substituting- th« 
above in formula 95, we obtain 

89000 X 323 

/. H. P. =: := 22.3 

60 X 33000 X .65 

Work out the value of hf by formula 70 and see how 
nearly it checks with the above.. 

165. Boilers: — A number of boilers will necessarily be 
installed in a plant of th'n kind, and a good arrangement is 
to have them so piped with water and steam headers that 
any number of the boilers may be used for steaming pur- 
poses and the rest as water heaters. They should also' b© so 
arranged that any of the boilers may be thrown out of 
service for cleaning or repairs and stili carry on the work 
of the plant. By doing this the boiler plant becomes very 
flexible and each boiler is an independent unit. Any good 
water tube boiler would serve the purpose, both as a steam- 
ing and as a heating boiler. Where the boilers are used as 
heaters, the water should enteir at the bottom and come out 
at the top. Where the water enters at the top and comes 
out at the bottom, the excessive heating of the front row of 
tubes retards the circulation of the water by ithis heat, and 
produces a rapid circulation through the rear tubes where the 
heat is the least. This rapid circulation in 'the rear tubes is 
not a detriment, but it is less needed there than in the front 
ones. It would be decidedly better if the rapid circulation were 
in the front row, causing the heat from the fire to be carried 
off more readily, and by this means giving less danger of 
burning the tubes. In the latter case the forced circulation 
from the pumps will be aided by the natural circulation 
from the heat of the fire, and the life of all the tubes then 
becomes more uniform. Fig. 118 shows a typical header 
arrangement. 

Boilers are usually classified as fire tube and water tube. 
Fire tuhe boilers are usually of the multitubular type, having 
the flue gases passing through the tubes and water sur- 



252 HEATING AND VENTILATION 

rounding them. Water tube boilers have the water passing- 
through ithe tubes and the flue gases surrounding them. 
The heating surface of a boiler is composed of those boiler 
plates having the heated flue gases on one side and the water 
on the other. A boiler horse-power may be taken as follows: 

Centennial Rating. 
One B. E. P. = 30 pounds of water evaporated from feed 
water at 100'' P. to steam at 70 pounds gage pressure. 

A. S. M. E. Rating. 

One B. H. P. = 34.5 pounds of water evaporated from 
and at 212° P, 

In laying out a boiler plant some good approximations 
for the essential details are: 

One B. H. P. = 11.5 square feet of heating surface 

(multitubular type). 
One B. H. P. = 10 square feet of heating surface 

(water tube type). 
One B. H. P. — .33 square foot of grate surface 

(small plant, say O'ue boiler). 
One B. H. P. = .25 square foot of grate surface 

(medium sized plant, say 500 H. P.). 
One B. H, P. = .20 square foot of grate surface 

(large plants). 
Pounds of water evapotrated per square foot of heating" 
surface per hour = 3 (approx. va'lue). 

166. Square Feet of Hot Water Radiation that can be 
Supplied on a Zero Day by One Boiler Horse-Povier when the 
Boiler is Used as a Heater: — Assuming that the coal used in 
the plant has a heating value of 13000 B. t. u. per pound, 
and that the efficiency of the boiler is 60 per cent., each 
pound of coal will transmit to the Wiater 7800 B. t. u. Since 
each pound of water takes up 25 B. t. u. on its passage 
through the heating boiler, one pound of coal will heat 312 
pounds, or 37.5 gallons -of water. This is equivalent to 
supplying heat, under extreme conditions of heat loss, to 
37.5 square feet of radiation for one hour. One boiler horse- 
power, according to Art. 165, is equivalent to the .expendi- 
ture of 969.7 X 34.5 = 33455 B. t. u. Now since each pound 
of -coal transfers to the water 7800 B. t. u., one boiler horse- 
power will require 33455 -f- 7800 = 4.28 pounds of coal. If, 
then, the burning of one pound of coal will supply 37.5 
square feet of hot water radiation for one hour, one boiler 



DISTRICT HEATING 253 

horse-power will supply 4.28 X 37.5 = 160 square feet for one 
hour, and a 100 H. P. boiler will supply 16000 square feet 
of water radiation in the district for the same time. These 
fig"ures have reference to boilers under good working con- 
ditions and probably give average results. 

167. Square Feet of Hot AVater Radiation in the District 
that can be Supplied on a Zero Day by an Economizer Lo- 
cated in the Stack Gases betyreen the Boilers and the Chim- 
ney: — In order to make this estimate it is necessary first to 
know the horse-power of the boilers, the amount of coal 
burned per hour, the pounds of gases passing through the 
furnace per hour and the heat given off from 'these gases 
to the circulating water through the 'tubes. 

Application. — Let C = pounds of coal burned per hour = 
boiler horse-power X pounds of coal per boiler horse-power 
hour, Wa = pounds of air passed through the furnace per 
pound of fuel burned, s == specific heat of the gases, tb = tem- 
perature of gases leaving boiler, ts =^ temperature of gases 
leaving economizer, tic =■ temperature of T\'ater entering 
economizer and tf ^temperature of T\'ater leaving the econo- 
mizer. Then, if 8.33 pounds of water will supply one square 
foot of radiation for one hour we have 

s X (0 X TFa + C) X (f& — ts) 
Bv, = ■ ■ (96) 

8.33 X {tf tu:) 

From a previous statement, 44500 pounds of steam per 
hour are generated in the steam boiler plant at a pressure 
of 125 pounds gage. To find the boiler horse-power let the 
total heat of the steam, above 32= at 125 pounds gage, be 
1191.8 B. t. u., and let the temperature of the incoming feed 
water to the boilers be 60 degrees. (In most cases the feed 
water will be at a higher temperature, but since it will occa- 
sionally be as low as 60 'degrees, this value will be a fair 
one.) The heat put into a pound of steam under these con- 
ditions is 1191.8 — (60 — 32) = 1163.8 B. t. u., and in 44500 
pounds it will be 51789100 B. t. u. Since one horse^power of 
boiler service is equivalent to 33455 B. t. u., we will need 
51789100 -^ 33455 = 1548 boiler horse-power. This horse- 
power will take care of all the engines and pumps rn -the 
plant. If the coal used contains 13000 B. t. u. per pound 
and the boilers have 60 per cent, efficiency, then 780Q B. t. u. 
Will be given to the water per pound of fuel burned, and 



254 HEATING AND VENTILATION 

the amount of coal burned per hour will be 51789100 -r- 7800 
= 6640 pounds. This gives 6640 -^ 1548 = 4.3 pounds of fuel 
per boiler horse-power hour, and 6.7 pounds of water evap- 
orated per pound of fuel. If the flue gases have 12 per cent. 
COo, there are used according to experiimental data, about 
21 pounds of air or 22 pounds of the gases of combustion, 
per pound of fuel burned. This is equivalent to 6640 X 22 
= 146080 pounds of flue gases total. Suppose now that these 
gases leave the furnace for the chimney at a temperature 
of 550 degrees F., that the economizer drops the tempera- 
ture of the gases down to 350 degrees (a condition which is 
very reasonable) and that the specific heat of the gases is 
about .22, we have 146080 X .22 X (550 — 350) = 6427520 
B. t. u. given off from the gases per hour in passing through 
the economizer (see numerator in formula 96). This heat 
is taken up by the circulating water in passing through the 
economizer toward the outgoing main. Now if the water, 
as it returns from the circulating system, enters the econo- 
mizer at 155 degrees, and leaves at 180 degrees, we will have 
6427520 -^ (180 — 155) = 257100 pounds of water heated per 
hour. This is equivalent to supplying 257100 ^ 8.33 = 30864 
square feet of radiation per hour when the plant is running 
at its peak load. Taking the "pounds of steam per hour" in 
the above as the only variable quantity, we are fairly safe 
in saying that the heat in the chimney gases from one horse- 
power of steaming boiler service will supply, through an 
economizer, 30864 -^ 1548 = 20 square feet of radiation in the 
district. In plants where only 7 pounds of water are allowed 
to each square foot of radiation per hour, .this becomes 23.8 
square feet of radiation instead. 

16S. Square Feet of Economizer Surface Required to 
Heat the Circulating Water in Art. 167: — Let E = the coeffi- 
cient of heat transmission through clean cast iron tubes and 
E ^ the efficiency of the tube surface Vv'hen in average serv- 
ice, also let the terms for the temperatures of the gases 
and the circulating water be as given in Art. 167, then 

Heat trans, per hour from gases to water 
Re = (97) 

/ /b + ts tf -i- tw \ 

^x^x{— ~) 

This formula assumes that the rate of heat flow through 
the tubes is the same at all points. As a m^atter of fact this 
rate changes slightly as the water becomes heated, but 



DISTRICT HEATING 255 

the error is not ^"orth mentioning- in such a formula, where 

the efnciency of the surface may be anything- from 100 per 

cent, in new tubes, to as low as 30 or 40 per cent, for old 

ones. 

Applicatiox. — Let K ^^ 1 and E =^ A, then 

6427520 

Re = — 8125 sq. ft. 

/ 550 + 350 180 + 155 \ 

^^•^n 2 ^-) 

With 12 square feet of surface per tube this gives 677 tubes. 

169. Square Feet of Economizer Surface to Install ^vhen 
the Economizer is to be Used to Heat the Feed Water for 
the Steaming Boilers: — If 30 pounds of feed water are fed 
to the boiler per ihorse-power hour, and if K =: 1, E = A, 
U = 550, ts = 350, tf = 250, and tw = 90 (about the lowest 
temperature at which water should enter the economizer), 
then the square feet of surface per horse-power is 

30 X (250 — 90) 

Re = = 6.1 sq. ft. 

/ 550 + 350 250 + 90 ' 

7 X .4 X ( 

\ 2 2 



) 



170. Total Capacity of the Boiler Plant and the Number 
of Boilers Installed: — The following discussion on the size 
of the boiler plant is purely for illustrative purposes and 
Is intended to show how such problems may be analyzed. 
In mos't cases the exhaust steam, and the economizer, if used, 
will f-all far short of supplying- the total radiation in the 
district, especially when the electrical output is light and 
the weather is cold. Suppose it be desired to install extra 
boilers to be used -as heaters for the radiation no't ^supplied 
from these two sources. To determine the amount of ex- 
tra boilers, find 'the amount of radiation to be supplied by 
the exhaust steam and the economizer and subtract this 
from the total radiation. The difference musit be supplied 
by boilers used as heaters. It is probably not safe to esti- 
mate too closely on the amount of exhaust steam given to 
the heating system. The maximum amount of 44500 pounds 
per hour was obtained, in this case, by pumping one gal- 
lon of water per hour for each square foot of radiation and 
by pumping city water, in addition to that obtained from 
the engines. In heating, a less amount of water than this 
may be circulated even on the coldest day. This is possi- 
ble, first, because water may be carried at a higher tem- 



256 HEATING AND VENTILATION 

perature than that stated, and second, because there may- 
be less loss of heat in the conduit, thus giving more heat per 
gallon of water to the radiation. Again, in estimating for 
a city water supply, the demands are not very constant and 
are difficult to estimate. In this one design it was thought 
that 44500 pounds per hour was a very liberal allowance 
and could be dropped to 35000 pounds (140000 square feet 
of radiation), when estimating the amount of radiation 
supplied by the exhaust steam. 

By Fig. 113 it will be seen that the minimum load on the 
steaming boilers carries through six hours out of the entire 
twenty-four and that the exhaust steam at this time drops 
to 22890 pounds per hour, supplying 91560 square feet of 
radiation. This minimum load is 51 per cent, of the max- 
imum, and 66 per cent, of the amount taken as an average, 
i. e., 35000. The work done by the economizer is fairly con- 
stant, .since the amount of economizer surface lost by the 
steaming boilers under minimum load would be made up 
by the additional heating boilers 'thrown into service. On 
the l)asis of 35000 pounds per hour, the exhaust steam and the 
stack gases together would heat 170960 square feet and 
there would be left 13540 square feet (184500 — 20 X 1548 
— 4 X 35000), to be heated by additional boilers. Under 
minimum load this would be approximately 122500, leaving 
62000 square feet to be heated by additional boilers. If one 
boiler horse-power supplies .160 square feet of radiation, 
then it would require 84 and 387 boiler horse-power re- 
spectively to supply the deficiency and the total horse-power 
needed In each case would be 1632 and 1935. A more satis- 
factory analysis, however, is the following which is worked 
on the lasts of 44500 pounds per hour. 

Let Ws = total number of pounds of steam used in the 

plant per hour = approximate number of pounds of exhaust 

steam available for heating the circulating water per hour; 

We = equivalent number of pounds of steam evaporated from 

and at 212°; X = total heat, above 32°, in one pound of dry 

steam at the boiler pressure; q' = total heat, above 32°, in 

one pound of feed water entering the boiler; then, if the 

latent heat of steam at atm'ospheric pressure = 969.7 B. t. u., 

we have 

Ws (X — q') 

We = (98) 

969.7 



DISTRICT HEATING 257 

and the corresponding boiler horse-power needed as steam- 
ing boilers will be 

We 

Bs. H. P. = (99) 

34.5 

Next, the radiation in the district that can be supplied 
by the exhaust steam is Rw = 4 TVs, and the amount sup- 
plied by the economizer is Re = 20 X B. E. P. From which 
we may obtain the capacity of the heating bailers, as 

Total Radiation — i Ws — 20 B. H. P. 

Bu: H. P. — ■ (100) 

160 

The total boiler horse-power of the plant is, therefore, the 
sum of Bs. H. P. and Bic. H. P. To obtain formula 100 for any 
specific case one must consider the maximum and minimum 
comdiitions of the steaming boiler plant. Let TTs (max) = 
miaximum exhaust steam, and TFs (min) = minimum exhaust 
s-team. Then for the two following conditions we have, 
Case 1, icliere the steaming and heating toilers are independent of 
each other, the total boiler horse-power installed = Bs. H. P. 
+ [totar radiation — 4 TTs (min) — 20 X 5. H. P. in use] -r- 
160. Also, Case 2, where a part or all of the steaming boilers are 
piped for both steaming and ivater service^ the total boiler horse- 
power installed — Bs. H. P. + [total radiation — 4 TFs (max) 
~ 20 X B. H. P. in use] ^ 160. It will be noticed that ithe last 
term representing the economizer service is simply stated 
as boiler horse-power and no distinction is made between 
steaming or heating service. This term is difficult ito esti- 
mate to an exact figure because it should be the total horse- 
power in use at any one time, both steaming and heating, 
and this can onlj^ be obtained by approximation. It makes 
no difference what service the boiler may be used for, the 
work of the economizer is practically the same. Probably 
the most satisfactory way is to substitute the value of 
Bs. H. P. for B. H. P. in the economizer and get the approxi- 
mate total horse-power, then if this approximate total horse- 
power differs very much from that actually needed, other 
trials may be made and new values for the total horse-power 
obtained until the equation is satisfied. 



258 HEATING AND VENTILATION 

Application. — Let Ws =■ pounds of exhaust s'team, \ = 
1191.8 (125 pounds gage pressure), and (/ = 28 (feed water 
at 60°); then when Ws = 44500 

VTe = 53400 

Bs. n. p. = 1548 

184500 — 4 X 22890 — 20 X 1548 

Bu. 77. P. Case 1 = = 387 

160 

184500 — 4 X 44500 — 20 X 1548 

Bw. H. P. Case 2 = = —153 

160 

This shows that there is an excess of waste heat in Case 2, 
making a total boiler horse-power, Case 1, = 1935 and Case 
2, = 1548. Investigating Case 1 to see what error w^as intro- 
duced by using 1548 in the economizer, we find approximately 
800 horse-power of steam boilers in use, and the total horse- 
power to be 1187, which is about 360* horse-power on the 
unsafe side. Substitute again and check results. Case 2 is 
reasonably close. In any case 'the most economical size of 
boiler plant to install in a plant requiring both steaming and 
heating boilers is one where at least a part, if not all, of the 
boilers are piped so as to be easily changed from one system 
to the other. By such an arrangement the capacity may be 
made the smallest possible. After obtaining the theoretical 
size of the plant, it would be well to allow a small margin 
in excess so that one or two boilers may be thrown out of 
oommiission for repairs and cleaning without interfering 
with the working of the plant. Case 2 seems to be the better 
arrangement. Assuming 1800 total boiler horse-power we 
might very well put in six 300 H. P. boilers arranged in three 
batteries. 

171. Cost of Heating from a Central Station (Direct 
Firing:): — It will be of interest in 'this connection to estimate 
approximately the cost in supplying heat by direct firing to 
one square foot of hot water radiation per year from the 
average central station. In doing this make the boiler as- 
sumptions to be the same as Art. 166. Take coal at 13000 
B. t. u. per pound, 2000 pounds per ton, and a boiler effi- 
ciency of 60 per cent. Water enters the boiler at 155 degrees 
from the returns, and is delivered to the mains at 180 de- 
grees. From the value of the coal as stated, we have 
15600000 B. it. u. per ton given off to the water. This is 



DISTRICT HEATING 



259 



Qri' 



6 



^ 



EXPANSION .' ^ 



tank( 







¥"ir 



-:^f-v 



tr- 



I 



5 



17771 



III III M Mill 




ECONOMIC ER 



S^P 



or 



^ 
h,^ 



POWER PLANT LAYOUT. 
Fig. 118. 



260 HEATING AND VENTILATION 

equivalent to heating- 624000 pounds, or 74910 gallons, of 
water. If one ton of coal costs $2.00 at the plant, we have 

200 -^ 74910 = .0027 cents 

This represents the amount paid to reheat one gallon of 
water, or to supply one square foot of heating" surface one 
hiour at an outside temperature of zero- degrees. Take the 
average temperature for the seven cold months at 32 de- 
grees. This is the average for the coldest year in the twenty 
years preceding 1910, as recorded at the U. S. Exp. Station, 
LaFayette, Indiana. We then have an average difference 
between the inside and the outside temperatures in any 
residence of 70 — 32 == 38. Tliis makes the formula for 
the heat loss, Art. 28, reduce to 38 -^ 70 == .54 of its former 
value. Now, if it takes one gallon of water per square foot 
of radiation per hour under maximum conditions, we have 
for the seven months .54 X 7 X 30 X 24 = 2722 gallons of 
water needed for each square foot of radiation per each 
heating year. This is equivalent to 2722 X .0027 = 7.35 cents 
per square foot of radiation for the heating year of seven 
months. 

T\"hen the plant is working under the best conditions 
this figure can be reduced. It can be done with boilers 
of a higher efficiency than that stated, or by using a cheaper 
coal, both of which are possible in many cases. 

172. Cost of Heating from a Central Station, Summary 
of Tests: — The following tests were conducted upon the 
Merchants Heating and Lighting Plant, LaFayette, Ind. ; one 
in 1906 and the other in 1908. The plant was changed slight- 
ly between the two tests and 'the radiatloin carried upon the 
lines was much increased, although in all essential features 
the plant was the 'Same. The circulating water was heated 
by exhaust steam heaters and by heating boilers. 

The plant had the following important pieces of appara- 
tus employed in generating or absorbing the heat supply: 

BOILERS (Steaming and Heating). 

Two 125 H. P. Stirling boilens. Total heating surface 
2524 sq. ft. 

Three 250 H. P. Stirling boilers. Total heating surface 
7572 sq. ft. 

Pressure on steam boilers (gage), 150 lbs. 

Pressure on heating boilers (approx.), 60 lbs. 



DISTRICT HEATING 261 

ENGINES. 

One 450 H. P. Hamilton Corliss comp. engine, direct con- 
nected to a 300 K. TT, Western Electric 72-pole alternating 
current generator 120 R. P. M. This engine carried the load 
of the plant when it was above 50 K, W., which was generally 
from 5:30 A. M. to 11:30 P. M. When this unit was run, direct 
current was obtained by passing the alternating current 
through a motor generator set. 

One 125 E, P. Westinghouse comp. engine, belted to one 
75 K. W. 3-phase alternating and two direct current genera- 
tors, and run at 312 R. P. M. This unit was generally run 
between 11:30 P. M. -and 5:30 A. M. 

One 250 H. P. Westinghouse comp. engine, belt connected 
to a 200 K. W. generator and two smaller machines. 

PUMPS. 
One centrifugal, two-stage pump, Dayton Hydraulic Co., 
direct connected to a Bates vertical high speed engine at 300 
R, P. M. 

Two Smith-Vaile horizontal recip. duplex pumps 14 in. 
X 12 in. X 18 in. Each of the three pumps connected to the 
return main in such a way as to be able to use any combina- 
tion at any one time to circulate the water. The centrifugal 
pump had been in service only one season. It had a capacity 
about equal to the two reciprocating pumps and under the 
heaviest service this pump and one of the duplex pumps 
were run in parallel. 

One Smith-Vaile horizontal reciprocating tank pump 
6 in. X 4 in. X 6 in. to lift the water of condensation from 

the exhaust heater to the tank. 

One Smith-Vaile horizontal reciprocating make-up pump 
6 in. X 4 in. X 6 in. to replace the water that was lost from 
the system. 

Two National horizontal reciprocating boiler feed pumps. 

One 9^ in. Westinghouse air pump, to keep up the sup- 
ply of air through the conduits to the regulator system in 
the heated buildings. 

One Deane vertical deep well pump, to deliver fresh 
water to the supply tank. 

One Baragwanath exhaust steam heater or condenser, 
having 1000 sq. ft. of heating surface. 



262 



HEATING AND VENTILATION 



PARTIAL. SUMMARY OF RESULTS. 

1906 1908 

1. Square feet of radiation 118000 150000 

2. Temperature of circulating water in 

degrees P., flow main 158.36 164.4 

3. Temperature of circulating water in 

degrees P., return main 139.9 139.6 

4. Temperature of circulating water in 

degrees P., after leaving heater 145.6 147. 

5. Temperature of outside air in de- 
grees P 32.6 37.5 

6. Temperature of stack gases in de- 
grees P., s.teaming boiler 566.8 

7. Temperature of stack gases in de- 
grees P., heating boiler 562, 656. 

8. Draft in stacks (all bolilers averaged) 

in inches of water .689 .595 

9. Heating value of coal in B. t. u. 

per pound 12800 11565 

10. B. t. u. delivered to steaming boiler 

per hour by coal 18187000 25833000 

11. B. t. u. delivered to heating boilers 

per hour by coal 19226000 27917000 

12. B. t. u. delivered to circulating water 

by heating boilers per hour 11800000 15405000 

13. B. t. u. to be charged to heating boil- 
ers (Item 12— Item 15) 7650000 6934000 

14. B. t. u. delivered to circulating water 
by exhaust steam from the gener- 
ating engines per hour 3600000 6602000 

15. B. t. u. thrown away during test 
from pump exhausts and available 

for heating circulating water 4150000 8471000 

16. B. t. u. available for heating circu- 
lating water from all exhaust steam 
as in normal running (Item 14 + 

Item 15) 7750000 15073000 

17. Total B. t. u. given to circulating 

water per hour (Item 13 + Item 16) .. 15400000 22007000 

18. Gallons of water pumped per hour 

[Item 17 -j- (8.33 X Items 2—3)] 100000 108000 



DISTRICT HEATING 263 

Id. Callons of waiter pumped per square 
foot of radiation per hour (Item 18 
H- Item 1) .85 .70 

20. Efficiency of heating boilers (Item 

12 -^ Item 11) approx .60 .55 

21. Value of the coal in cents per ton of 

2000 pounds at the plant 200. 175. 

22. Average electrical horse-power 68 141 

'Note. — The above values are averages and were taken 
for each entire test. The B. t. u. values were considered 
satisfactory when approximated to the nearest thousand. 

173. Regulation: — The regulation of the heat within the 
residences is best controlled from the power plant. In most 
heating plants a schedule is posted at the power house which 
tells the engineer the necessary temperature of the circu- 
lating water to keep the interior of the residences at 70 
degrees with any given outside temperature. The Merchants 
Heating and Lighting Company mentioned above use the 
following schedule: 

Atmosphere Water Atmosphere Water 

i60 deg. 120 deg. 10 deg. 190 deg. 

50 " 140 " •* 200 " 

40 " 150 " —10 " 210 " 

30 " 160 " — 20 " 220 " 

20 ** 180 " 

In addition, read the article by Mr. G. E. Chapman, pub- 
lished in the Heating and Ventilating Magazine, August 
1912, page 23, in which he describes the methods used in 
regulating the Oak Park, 111. plant. 

In some heating plants the regulation is by means of air 
carried from the compressor at the power house through a 
main running parallel with the "w^ater mains in the conduits 
and branching to each building where it is used under a 
pressure of 15 pounds to operate thermostats, which in turn 
control the water inlets to 'the radiators. A closer regula- 
tion 'is obtained in the latter system than in the former, but 
i* LS needless to say that the 'thermostats require careful 
adjustments and frequent inspections. 

Diaphragms or chokes having different sized orifices may 
be placed on the return main from each building to regulate 
the supply. Those buildings nearest to the power plant 
have the advantage of a greater differential pressure than 



264 HEATING AXD VENTILATION 

those farther away, hence should have smaller diaphragms. 
By increasing" the resistance in the return line from any 
building the water circulates more slowly and has time to 
give off more heat to the rooms. W^th a high temperature 
of the water and a careful adjus-tment of the diaphragms 
it is possible to have the amount of water circulated per 
square foot of radiation reduced much below one gallon per 
square foot per hour. 

STEAM SYSTEMS. 

174. Heating by steam from a central station, compared 
with hot water heating, is a very simple process. The power 
plant equipment is composed of a few inexpensive parts, the 
operation of which is very simple and easily explained. 
These parts have but few points that require rational de- 
sign. Because of the simplicity and the similarity to the 
preceding discussion on hot water systems, the work on 
steam systems will be very brief. All questions referring- 
to the construction of the conduit, the supporting of the 
pipes, the provision for contraction and expansion, the drain- 
Ung of the pipes and conduits, are common to both hot 
water and steam systems and are discussed in Arts. 138 and 
139. A large part of the work referring directly to district 
hot water heating applies with almost equal force to steam 
heating. This part of the work, therefore, will deal with 
such parts of the power plant equipment as differ from 
those of the hot water system. 

Steam heating may be classified under two general 
heads, high pressure and low pressure. A very small part 
of the heating in this country is now done by what may be 
strictly called high pressure service, i. e., where radiators or 
coils are under pressures from 30 to 60 poun<is gage, and 
this small amount is gradually decreasing. Ordinarily, 
steam is generated at high pressure at the boiler, 60 pounds 
to 150 pounds gage, and reduced for line service to pressures 
varying from to 30 pounds gage, with a still further re- 
duction at the building to pressures varying from to 10 
pounds gage, for use in radiators and coils, "^"here exhaust 
steam is used in the main, the pressure is n^ot permitted to 
go higher than 10 pounds gage, because of the back pres- 
sure on the engine piston. Where exhaust steam is not 
used, the pressures may go as high as 30 pounds gage, thus 
allowing for a greater pressure drop in the line and a corre- 



DISTRICT HEATING 



265 



sponding" reduction in pipe sizes. Vaciiitm returns may be ap- 
plied to central station work the same as to isolated plants. 

The principles involved in the power plant end of a 
steam heating- system may be represented by Fig-. 119. It 
will be seen that the exhaust steam from the engines or tur- 
bines has four possible outlets. Pasisiing- throug-h the oil 
separator, which removes a large part -of the entrained oil, 
part of the exhaust steam is turned into the heater for use in 
heating the boiler feed water. The rest of the steam passes 
on into the heating system. If there be more exhaust steam 
than is necessary to supply the heating system, the balance 
may go to the atmosphere through the back pressure valve. 
When the heating system is nott in use, as would be the case 
in the four warm rmonths of the year, the exhaust isteam may 
be passed into the condenser. 



BYPASS AROUND HEATETR 

TO Backpressure valve 



TOHETATER AND 
BACK PRESS VALVE 



TDCONDENSCR 



eparator 



CHEATING 
SY3TEM 



TO SEWER 

STEAM TRAP 




LIVE 3TEAM 
EROM BOILERS 



Fig. 11 



It is very evident, from what has been said before, that 
it would not be economical to condense the steam in a 
condenser as long as there is a posisibility of using it in the 
heating system. The increased gain in efficiency, when con- 
densing the exhaust steam under vacuum, is very ismall com- 
pared to the giain when this same steam is used foT heating 
purpoises. It ^lould be also very poor eooinomy to use any 
live steam for heating when there were any exhaust steam 
wasted. When the am,ount of exhaust isteam -is dnisufficient, 
live siteam is admjitted through a pressure reducing" valve. 

175. Drop in Pressure and the Diameter of the Mains:— 
The flow of steam in a pipe follows the same general law as 



266 HEATING AND VENTILATION 

the flow of water. The loss of head may be represented 
by the well known formula 

Jif = (101) 

g d 

w/here hf = loss of head in feet, (p = coefRaient of friction, 
V = veloci'ty in feet per second, I = length of pipe in feet, 
d =^ diiameteir of the pipe in feet 'and g = 32.2. Substitute, 
Jif = 144 p -^ D, Where p = drop in pressure in pounds and 
D = density of the -steam, and find 

, 2 dylv^D 

p = (102) 

mgd 

The coefficient of friction is found to vary wlith the velocity 
'of the steam and with the diameter of the pipe. Prof. Unwln 
found that for velocities of 100 feet per second (good prac- 
tice for transmiission lines), it could be expressed as follows, 
where c is a constant to be found by expeniment, 



ci> = c ( 1 + ) 

\ 10 d / 



which, when substituted in foirmula 102, gives 



V lOd / 



Iv^D c / 3 

P = ( 1+ I (103) 

12 gd 



Let W = pounds of steam passing p£r minute and di = diam- 
eter of pipe in inches, then 

1 / 3.6 \ TF^Zc 

P = ^ ( 1+ I (104) 

20.663 V di / dt^D 

From this formula we may obtain any one of the -three terms, 
W, dx or p, if the other two are known. Table 36, Appendix, 
was compiled from formula 104 with c = .0027. For discus- 
sion, see Trans. A. S. M. E., Vol. XX, page 342, by Prof. R. C. 
Carpenter. Also Encyclopedia Britannica, Vol. XII, page 491. 
See also, Kent, page 670, and Carpenter's H. & V. B., page 51. 
It will be seen that Table 36 is compiled upon the basis 
of one pound pressure drop, at an average pressure of 100 
pounds absolute in the pipe. Since in -any case the drop 
in pressure is proportional to the square of the pounds of 
steam delivered per minute (pther terms »rem<aining con- 
stant), the amount delivered at any other pressure drop 
than that given (one pound) wQuld be fo^ncj by multiplying 



DISTRICT HEATING 26V 

the amount g-iven in the table by the square root of the 
desired pressure drop in pounds. Also, sdnce the weight of 
■steam moved at the same velocity, under any other absolute 
pressure, is approximiately proportional to the absolute pres- 
sures (other terms remaining constant), we hiave the 
amount of steam moved under the given pressure, found by 
multiplying the amount given in the table by the square 
root of (the ratio of the absolute pressures. To illustrate the 
use of the table — suppose the pressure drop in a 1000 foot 
run of 6 dnch pipe is 8 ounces, when the average pressure 
within the pipe is 10 pounds gage. The amount -of steam 



carried per minute is 93.7 X V.5 -h V^OO -^ 2o = 33 pounds. 
Or, if the drop is 4 pounds, at an average inside pressure of 
50 pounds gage, the amount carried would be 150 pounds 
per minute. Conversely — find the diiameter of a pipe, 1000 
feet long, to carry 150 pounds of steam per minute, at an 
average pressure of 50 pounds gage and a pressure drop of 
8 ounces. 



150 /lOO 

W (table) = __ X ^ = 264 pounds 

V.5 \ 65 



which, according to the table, gives a 9 inch pipe. 

176. Drippingr the Condensation from the Mains: — The 

condensation of the steam, which takes place In the con- 
duit mains, should be dripped to the sewer oir the return 
at centain 'specified points, through siome form of steam 
trap. These traps sihould be kept in first clas<s eoindition. 
They should be inspected every seven or ten days. No pipe 
should be drilled and tapped for this water drip. The only 
satisfactory way is to cut the pipe and insert a tee with 
the branch Looking downward and leading to the trap. The 
sizes of the traps and the distances between them can only 
be determined when the pounds of condensation per running 
foot of pipe can be estimated. 

177. Adaptation to Private Plants: — Distrlict steam 
heating systems miay be adapted to private hot water plants 
by the use of a "transformer." This in principle is a hot 
water tube heater which takes the place of the hot water 
heater of the system. It may also be adapted to warm air 
systems by putting the steam through indirect coils and 
taking the air supply from over the coils. 



268 HEATING AND VENTILATION 

178, General Application of the Typical Design: — The 

following" brief applications are meant to be sug-gestive of 
the method only, and the discussions of the various points 
are omitted. 

Square feet of radiation in the district. — 

Rs = 184500 X 170 -^ 255 = 123000 square feet. 

Amount of heat needed in the district to supply the radiation for 
one hour in zero tceather. — 

Total heat per houT = 123000 X 255 = 31365000 B. t. u. 

Amount of heat necessary at the power plant to supply the radia- 
tion for one hour in zero weather. — Assuming 15 per cent, heat 
loss in the conduit (this is slightly less than that allowed for 
the hot water two-pipe system, 20 per cent.), we have 
31365000 -^ .85 = 36900000 B. t. u. per hour. 

Total exhaust steam available for heating puri)oses. — 

Ws (max.) = (23100 + 8680) X 1.15 = 36547 pounds per hour. 
Ws (man.) = ( 1490 + 8680) X 1.15 = 11696 pounds per hour. 

Total B. t. u. available from exhaust steam per hour for heating.^ 
Let the average pressure in the line be 5 pounds gage and 
let the w^ater of condensation leave the indirect coils in the 
residences at 140 degrees. We then have from one pound of 
exhaust steam, by formula 72, 

B. t. u. — .85 X 960 + 195.6 — (140 — 32) = 903.7 
Assuming this to be 900 B. t. u. per pound, the total available 
heat from the exhaust steam for use in the heating system 
is, maximum total == 32892300 B. t. u. and the minimum total, 
= 10526400 B. t. u. 

Square feet of steam radiation that can be supplied by one pound 
of exhaust steam at 5 pounds gage. — 

Rs = 900 -^ (255 -J- .85) = 3. 

Total B. t. u. to be supplied by live steam. — 
B. t. u. (max. load) = 36900000 — 32892300 = 4007700 B. t. u. 
B. t. u. (min. load) = 36900000 — 10526400 = 26373600 B. t. u. 

Total pounds of live steam necessary to supplement the exhaust 
steam. — Let the steam be generated in the boiler at 125 
pounds gage. With feed water at 60 degrees 

Max. load = 4007700 -h 1163.8 = 3444 pounds. 

Min. load = 26373600 -^ 1163.8 = 22661 pounds. 



DISTRICT HEATING 



Boiler Tiorse-poiccr needed for tJie steam power units. — As in 
Arts. 167 and 170, 

Bs. H. P. (max.) = 36547 X 1.2 -^ 34.5 = 1271. 
Bs. H. P. (min.) = 11696 X 1.2 -^ 34.5 = 407. 
Total boiler horse-power needed in the plant, — .Maximum load. 
B. H. P. (to.tal) = 1271 + (3444 X 1.2 -t- 34.5) = 1391. 

It will be noticed that this total horse-power is 157 
horse-power less than the corresponding" Case 2 in Art. 170. 
This is accounted foT by the fact that no steam is used up in 
work dn the circulating- pumps, also that the conditions of 
steam generation and circulation are slightly different. 1500 
boiler horse-power would probably be installed in this case. 

Size of conduit mains. — Let it be required to find the 
diameters of the main system in Fig. 115 at the important 
points shown. Art. 147 gives the length of the mains in each 
part. Allow .3 pound of steam foir each square fo'Ot 'Of steam 
radiation per hour Othis will no doubt be sufficient to supply 
the radiation 'and conduit losses). Try first, 'that part of the 
line between the power plant -and A, with an average .steam 
pressure in the lines of about 5 pounds gage 'and a drop in 
pressure of 1^ ounces per each 100 feet of run (approxi- 
mately 5 pounds per mile). 25200 pounds per hour gives 
W — 420. The leng,th of <this part of the line is 200 feet and 
the drop is 3 ounces, or .19 pound. 



W (table) = 



420 



- X 



V.19 






2158 pounds 



which gives a 15 Inch pipe. 

Following 'Out the same reasoning for all parts of the 
line, we have 

TABLE XXVIII. 

i P P to A I A to B I B to C I C to D | D to E 



Distance between points 

Radiation supplied, sq. ft 

Pressure-drop in pounds = p 

Diameter of pipe in inches, by table... 



200 


500 


1500 


1500 


84000 


57000 


34000 


19000 


.19 


.47 


1.4 


1.4 


15 


13 


11 


9 



500 
8000 
.47 
5 



In general practice, these values would probably be 
taken 16, 14, 12, 10 and 6 inches respectively. Look up 
Table 36, Appendix, and check the above figures. 



270 HEATING AND VENTILATION 

REFERENCES. 
References on District Heating. 

Technical Books. 

Allen, Notes on Heafing and Ventilation, p. 131. 
Gifford, Central Station Heating. 

Technical Periodicals. 

Engineering News. Comparison of Costs of Forced-Circula- 
tion Hot Water and Vacuum-Steam Central Heating" Plants, 
J. T. Mag-uire, Dec. 23, 1909, p. 692. Desig-n of Central Hot- 
Wiater System with Forced-Circulation, J. T. Maguire, Sept. 
2, 1909, p. 247. Engineering Review. Determining Depreciation 
of Underground Heating Pipes, W. A. Knight, Jan. 1910, 
p. 85. Some Remarks on District Steam Heating, W. J. Kline, 
April 1910, p. 61. Toledo Yaryan System, A. C. Rogers, May 
1910, p. 58. Some of the Factors that Affect the Cost of 
Generating and Distributing Steam for Heating, C. R. Bishop, 
Aug. 1910, p. 56. Central Station Heating Plant at Craw- 
fordsville, Ind., B. T. Gifford, Dec. 1909, p. 42. Wilkesbarre 
Heat, Light and Motor Co., A Live Steam Heating Plant, 
J. A. Wihite, July 1908, p. 32. The Heating and Ventilating 
Magazine. Schott Systems of Central Statio-n Heating, J. C. 
Hornung, Nov. 1908, p. 19. Data on Central Heating Sta- 
tions, Nov. 1909, p. 7. Cost of Heat from Central Plants, 
March 1909, p. 31. Steam Heating- in Connection with Cen- 
tral Stations, Paul Mueller, Oct. 1909, p. 24; Nov. 1909, p. 1. 
A Modeirn Central Hot Wlater Heating- Station, W. A. Wolls, 
July 1910, p. 15. Central Station Heating, F. H. Stevens, June 
1910, p. 5. The Profitable Operation of a Central Heat- 
ing Station without the Assistance of Electrical or Other 
Industries, Byron T. Gifford, Aug. 1910. Central Station 
Heating, Byron T. Gifford, Apr. 1911. Central Power and 
Heating- Plant for a Group of School Buildings, May 1910. 
Domestic Engineering. Report of Second Annual Conven- 
tion of the National District Heating- Association at 
Toledo. O., June 1, 1910. Vol. 51, No. 11, June 11, 1910, p. 255. 
The Metal Worker. Central District Steam Heating from 
Hill Top, Jan. 15, 1910, p. 78. Central Heating at Crawfords- 
ville, Ind., July 30, 1910, p. 135. Data of 77 Central Station 
Heating Plants, Sept. 4, 1909, p. 48. Hot Water Heating, 
Teupitz, Germany, Sept. 25, 1909, p. 45. High Pressure 
Steam Distribution, Munich, Germany, Oct. 2, 1909, p. 48. 
Central Plant Solely for Residence Oct. 16, 1909, p. 50. 
Two Types of Central Heating Plant Compared, Apr. 9, 1910. 
Central Heating at Crawfordsville, Indiana, July 30, 1910. 
The Engineering Record. District Heatiing, July 15, 1905. Econ- 
omies Obtainable by Various Uses of Steam in a Combined 
Power and Heating Plant, Feb. 18, 1905. A Study for a 
Central Power and Heating Plant at Washington, Feb. 11, 
1905. Utilization of Vapor of Steam Heating Returns, Oct. 
22, 1904. A Central Heating, Lighting and Ice-Making Sta- 
tion, Gulfport, Miss., Feb. 27, 1904. Purdue University Cen- 
tral Heating and PO'Wer Station, Jan. 30, 1904. A Central 
Hot-Water Heating- Plant in the Boston Navy Yard, July 
16, 1904. Power. Combined Central Heating- and Electric 
Plants, Edwin D. Dreyfus, Aug. 20, 1912. 



CHAPTER XIV. 



TE3IPERATrRE CONTROL IX HEATING SYSTE3IS. 



179. From tests that have been conducted on heating" 
systems, it has been shown that there is less loss of heat 
from buildings supplied by automatic temperature control, 
than from buildings where there is no such control. A uni- 
form temperature within the building- is desirable from all 
points of view. Where heating systems are operated, even 
under the best conditions, without such control, the effi- 
ciency of the system would be increased by its application. 
No definite statement can be made for the amount -of heat 
saved, but it is safe to say that it is between 5 -and 20 per 
cent. A building uniformly heated during the entire time, 
requires less heat than if a certain part or all of the build- 
ing were occasionally allowed to cool off. When a building 
falls below normal temperature it requires an extra amount 
of heat to bring it up to normal, and when the inside tem- 
perature rises above the normal, it is usually lowered by 
opening windows and doors to enable the heat to leave rap- 
idly. High inside temperatures also cause a correspondingly 
increased radiation loss. Fluctuations of temperature, there- 
fore, are not only undesirable for the occupants, but they 
are very expensive as well. 

180. Principles of the System; — Temperature control may 
be divided into two general classifications, — small plants 
and large plants. The control for small plants, i. e., such plants 
as contain very few heating units, is accomplished by regu- 
lating the drafts by special dampens at the combustion 
chamber. This method controls merely the process of com- 
bustion and has no especial connection with individual reg- 
isters or radiators, it being assumed that a rise or fall of 
temperature in one room is followed by a corresponding 
effect in all the other rooms. This method assumes that all 
the heating units are very accurately proportioned to the 
respective rooms. The dampers are operated thr-ough a sys- 
tem of levers, which system in turn is controlled by a ther- 
mostat. Fig. 120 shows a typical application of such regu- 



272 



HEATING AND VENTILATION 




Fig-. 120. 



lation. This may be ap- 
plied to any system of 
heat. In addition to the 
thermostatic control 
from the room to the 
dampen, as has just been 
mentioned, closed hot 
water, steam and vapor 
systems should have 
•reg-ulation from the 
pressure within the 
boiler to the draft. Oc- 
casionally in the miorn- 
i n g- the pressure in 
either system may be- 
come excessive before 
the house is heated 
enoug-h for the thermo- 
stat to act. With such 
additional .reg-ulation no hot water heater or steam boiler 
would be forced to a dang-erous pressure. Fig. 121 shows a 
thermostat manufactured by the Andrews Heating Co., Min- 
neapolis. The complete regulator has in addi- 
tion to this, two cells of open circuit battery 
and a motor box, all of which illustrate very 
well the therm^ostatic damper control. 

The thermostat operates by a differential 
expansion of the two different metals com- 
posing- the spring- at the top. Any change in 
temperature causes one of the metals to ex- 
pand or contract more rapidly than the other 
and gives a vibrating movement to the project- 
ing arm. This is connected with the batteries 
and with the motor in such a way that when 
the pointer closes the contact with either one 
of the contact rosts, a pair of magnets in the 
motor causes a crank crm to rotate through 
180 degrees. A flexible connection between this 
crank and the damper causes the damper to 
open or close. A change in temperature in 
the opposite direction makes contact with the other post 
and reverses the movement of the crank and damper. The 
movement of the arm between the contacts is very ismall thus 




Fig. 121. 



TEMPERATURE CONTROL 



273 



making* the thermostat very sensitive. No work is required 
of the battery except that necessary to release the motor. 

Occasionally it is desira- 
able to connect small heat- 
ing- plants having only one 
thermo'Stat in control, to a 
central station system. Fig. 
122 showis how the supply 
of heat may be controlled 
by the above method. 

Fig. 123 shows the Syl- 
phon Damper Regulator 
made by The American 
Radiator Co., and applies 
to steam pressure control. 
The longitudinal expansion 
of a corrugated brass or 
copper cylinder operates 
the damper through a sys- 
tem of levers. The longitu- 
dinal movement of the cyl- 
inder is small and hence 
the bending of the metal 
in the walls of the cylinder 
is very slight. This small 
movement is multiplied 

Fig. 122. 





Fi^. 123. 



274 



HEATING AND VENTILATION 



through the system of levers to the full amount necessary 
to operate the damper. A similar device is made fcy the 
same company for application to hot water heaters. 

Temperature control in large plants^ i. e., those plants having 
a Large number of heating units, is much more complicated. 
In furnace systems this is very much the same as described 
under small plants, with additional dampers placed in the 
air lines. The following discussions, therefore, will apply 
to hot water and steam systems, land will be additional to the 
control at the heater and boiler as discussed under small 
plants. Fig. 124 shows a typical layout of s^ch a system. 
Compressed air at 15 pounds per square inch gage is main- 
tained in cylinder, Su, which is looaited in -some convenient 





Fig. 125. 



Fig. 124. 



place for the attendant. This air is car- 
ried to the therm'ostat, Th, on one of the 
protected walls in the room. Here it 
passes through a controlling valve and 
is then led to the regulating valve on the 
iradiator. This air acts on the top of a 
rubber diaphragm as shown in Fig. 125 
to close the valve and to cut off the sup- 
ply. When the room cools off, the con- 
trolling valve at Tix cuts off the supply 
and opens the air line to the radiator. 
This removes the air pressure above the 



TEMPERATURE CONTROL 275 

diaphrag-m and permits the stem of the valve to lift. On the 
opening" of the valve the steam or water again enters the 
radiator and the cycle is completed. 

Fig. 96 shows the application of the thermo-static control 
to the blower work. This shows the thermostat B and the 
mixing dampers, located at the plenum chamber, in the 
single duct system. The same general arrangement could 
be applied to the double duct system, with the dampers in 
the wall at the base of the vertical duct leading to the 
room. 

181. Some of the Important Points in the Installation:— 

Each radiator has its own regulating valve. All rooms 
having- three radiators or less are provided with one thermo- 
stat. Large roomys having four or more radiators have two or 
TnoTe therm'ostats wath not more than three radiators to the 
thermostat. Where other motive power is not available fo.r 
the air supply, a hydraulic compressor is used. This com- 
pres'sor automatically maintains the air pressure at 15 
pounds gage in the steel supply tank. The main air trunk 
lines are galvanized iron, % and Vz inch in diameter, and 
are tested under a pressure of 25 pounds gage. All branch 
pipes are i/4 and % inch galvanized iron. All fittings on 
the % inch pipes are usually brass. W'here flexible connec- 
tions are made, this is sometimes done by armoured lead 
piping. Thermiostats are usually pirovided with metallic 
covers, and are finished to correspond with the hardware of 
the respective rooms. Each thermostat is provided with a 
thermometer and a scale for making adjustments. Each 
radiator is provided with a union diaphragm valve having 
a specially prepared rubber diaphragm with felt protection. 
This valve replaces the ordinary radiator valve. One of 
these valves is used on the end of each hot water radiator, 
one on each one-pipe steam radiatoir and two on each two- 
pipe low pressure steam radiator. This last condition does 
not hold for two-pipe steam radiators with mechanical 
vacuum returns, in which case patented specialties are 
applied by the vacuum company. In such cases the s-upply 
to the radiator only is controlled. In any first class sys-tem 
of control, the temperature of the room may easily be kept 
within a maximum fluctuation of three degrees. 

182. Some Special Designs of Apparatus: — All tempera- 
ture control work is solicited by specialty companies, each 
having a patented sj-stem. In the essential features these 



576 



HEATING AND VENTILATION 



system's all agree with the foreg-oing general statements. 
The chief difference is in the principle upon which the ther- 
mostat, Til, operates. 



INTERMEDIATE 



POSITIVE 



B 



c 
















T 


-J 


to 
to 

< 


UJ 
U 


g 





Fig. 126. 

Fig. 126 shows section-s through the intermediate and 
po>sitive thermostats manufaKitured by the Jiohnso^n Service 
Company, Milwaukee. The interior workings of the ther- 
mostats are as follows: Intermediate. — Air enters at A from, 
the supply tank, passes into chamber B and escapes at port 
0. If thermostatic 'Strip T expands inward to close 0, the 
air pressure collects in B and presses down port valve F, 
thus opening port E, letting -air through into F and o^ut at Q 
to close the damper, ^^hen T expands outward, pressure at 
B is relieved and T is forced back by la spring, closing E. 
Air in F reacts against the diaphragm and escapes through 
hollow valve Y at H, permitting the daimper to open. Posi- 
live. — ^Air enters at A, passes into chamber B and escapes 
at C. If thermostatic strip T expands inward to close 0, air 
pressure collects in B, forces out the knuckle joint K and 



TEMPERATURE CONTROL 277 

operates the three-way valve T, thus shutting port E and 
opening" port F, letting air escape and radiator valve open. 
When T expands outward, pressure at B is relieved, knuckle 
joint K returns, pulling V outward, thus shutting port F, 
opening E, letting air escape through G and shutting off 
radiator valve. 

The real thermostat is the spring T. This is composed 
of steel and brass strips brazed together. Because of a 
higher coefficient of expansion in the brass than in the 
steel, a change in the room temperature causes the spring 
to move toward or away from the seat C T is 'adjustable 
for any desired room temperature. The intermediate ther- 
m.ostat is used on indirect heating where mixing dampers 
are employed and where an intermediate position of the 
valve is necessary. The positive therm'Osta.t is used on 
direct radiators and coils where a full open or full closed 
movement of the valve is desired. 

Fig. 127 shows a section through the pattern K theTmo- 
stat, manufactured by the Powers Regulator Co., Chicago. 
This thermostat consists of a frame carrying two corrugated 
disks, brazed together at the circumference and oontaining a 
volatile liquid having a boiling point at about 50- degrees F. 
At a temperature of about 70 degrees, the vapor within 
the disks has a pressure of about 6 pounds to the square 
inch. This pressure varies with every change of tempera- 
ture and produces variations in the total thickness at the 
center of the disks. 

The compressed air enters at H and passes into chamber 
W through the controlling valve J, which is normally held to 
its seat by a coil spring under cap P. Within the flange M 
is located an escape valve L upon w.hich the point of the 
supply valve J rests. Valve L tends to remain open when 
permitted by reason of the spring underneath the cap. Wihen 
the temperature rises sufficiently to cause the disks to in- 
crease in thickness and rruove the flange M, the fi<rst action 
is to seat the escape valve L, its spring being weaker than 
that above J. If. the expansive motion is continued after 
valve L is seated, the valve J is then lifted from its seat 
and compressed air flows into the chamber N. As the 
air accumulates in chamber N, it exerts a pressure upon the 
elastic diaphragm K in opposition to the expansive force of 
the disk. So, whenever there is sufficient pressure in A" to 
balance the power exerted by the disks, the valve J returns 



278 



HEATING AND VENTII.ATION 





Fig. 127. 



to its seat and no more air is permitted to pass through. 
If the temperature falls, the pressure within the disks be- 
comes less, the disks draw together and the over-balancing 
air presG'are in N reverses the movement of the flange M and 
permits the escape valve L under the influence of its spring 
to rise from its seat, whereupon a portion of the air in N 
is discharged until the pressure in N becomes equal to the 
diminished pressure from the disks. Thus the press-ure of 
the air in N is maintained always in direct proportion to the 
expansive power (temperature) of the disks. Port / con- 
nects with chamber N and leads to the diaphragm valve. 

This thermostatic valve controls the regulator valve by 
a graduated movement and is used on the dampers for 
blower work. Another form with maximum m^ovement only 
is designed for steam systems. 

Fig. 128 shows the positive and graduated thermostats 
as manufactured by the National Regulator Company, Chi- 
cago. The thermostatic element in these thermostats is the 
vulcanized rubber tube A, which changes its length with the 
varying room temperatures and causes the valve O to open 
or close the port G, thus controlling the supply of air to 



TEMPERATURE CONTROL. 



279 



POSITIVE 



INTERMEDIATE 





Fig. 128. 

and from the radiator valve or the regulating- damper. In 
the positive thermostat air enters the tube from the supply- 
through the filter and restricted passage P. From the in- 
terioir of the tube the air leaves through the middle orifice 
and enters the pipe leading to the radiator valve. If the 
room 'temperature is above the norm^al, port G closes and the 
air pressure collects in the tube, thus creating a pressure 
in the line leading to the radiator valve and closing it. If 
the room temperature falls below the normal, port G opens, 
air is exhausted from the tube to 'the atmosphere, the pres- 
sure on the radiator valve is released and the valve opens. 
The intermediate thermostat differs from the positive ther- 
mostat in having but 'One air line. Room temperatures 
below the normal contract tube A, open port G, and exhaust 
the air to the atniiosphere. With this release in pressure in 
the pipe at P the regulating damper is turned to admit 
more warm air into the room. W.ith the room temperature 
above the normal, tube A expands, port G closes, pressure in 
pipe P increases and the regulating damper is turned so as 
to admit 'a lower temperature of air in the room. By means 
of this a graduated movement of the damper Is obtained. 



REFERENCES. 

References on Temperature Control. 

Metal Worker. Temperature Control in House Heating, 
Jan. 7. 1911. ' ^ 



CHAPTER XV. 



ELECTRICAL. HEATING. 



In the present state of the heating- business it seems 
almost unnecessary to discuss electrical heating", in any 
serious way, in connection with steam power plants. The 
reasons will be seen in the following brief discussion. 
Electrical heating can appeal to the public only from the 
standpoint of convenience, since a comparison of economies 
between steam, hot water or warm air heating on one hand, 
and electrical heating on the other, is wholly against the 
latter. Its application to the processes of heating will find 
its greatest economy in connection with water power plants 
where the combustion of fuel is eliminated from the prop- 
osition. This discussion will not bear in any way upon the 
water power g-enerator. 

183. Equations Employed in Electrical Heatingr Design:-— 

1 H. P. = 746 watts. 

1 H. P. =: 33000 ft. lbs. permin. = 1980000 ft. lbs. per hr. 

1 B. t u. = 778 ft. lbs. 

1 H. P. hr. = 1980000 ^ 778 = 2545 B. t. u. per h«r. 

1 H. P. hr. = 746 watt hrs. = 2545 B. t. u. per hr. 

a watt hr. = 3.412 B. t. u. per hr. 

1 watt hr. = 3.412 -^ 170 = .02 sq. ft. of hot water rad. 

1 watt hr. = 3.412 -^ 255 = .0134 sq. ft. of steam rad. 

1 kilo-watt hr. = 20.1 sq. ft. of hot water rad. (105) 

1 kilo-watt hr. = 13.4 sq. ft. of steam rad. (106) 

184. Comparison bet^reen Electrical Heating and Hot 
Water and Steam Heating: — The loss in transmitting elec- 
tricity from the g-enerators through the switchboard to the 
radiators may be small or large, depending upon the condi- 
tions of wiring-, the current transmitted and the pressure on 
the line. In all probability it would equal or exceed the 
transmission losses in hot water or steam lines. Assuming 
these losses to be the same, a fair comparison may be made 
in the cost of heating by the various methods. The operat- 
ing eflficiency of an electric heater is 100 per cent., since all 



ELECTRICAL HEATING 281 

the current that is passed into the heater is dissipate! in 
the form of lieat and no other losses are experienced. This 
is not true of steam systems where the water of condensa- 
tion is thrown away at fairly high temperatures. Where 
electricity or steam is generated and distributed all in the 
same building-, there is no line loss to be accounted for, 
since all of this heat goes to heating the building and counts 
as additional radiation. 

Equations 105 and 106 show the theoretical relation 
existing between electrical heating and hot water and steam 
heating compared at the power plant. The following dis- 
cussion is based, therefore, upon the assumption that 1 
kilo-watt hour, in an electric radiator, will give off the same 
amount of heat as 20.1 and 13.4 square feet of hot water and 
steam radiation respectively. With coal having 13000 B. t. u. 
per pound and a furnace efficiency of 60 per cent., it will 
require 3412 -^ 7800 == .44 pound of coal per hour. If coal 
costs $2.00 per ton of 2000 pounds, there will be an actual 
fuel expense of .044 cent. On the other hand, assuming the 
combined mechanical efficiency of an engine or turbo-gener- 
ator set to be 90 per cent., the heat from the steam that is 
turned into electrical energy per hour is 1000 -^ .90 = 1111 
watts, for each kilo-watt delivered. Now if this unit has 
15 per cent, thermal efficiency, we have the initial heat in 
the steam equivalent to 1111 -4- .15 = 7400 watt hours. From 
this obtain 7400 X 3.412 = 25249 B. t. u. per hour; or, 25249 
-i- 7800 = 3.2 pounds of coal per hour. This, at the same 
rate as shown above, would be worth .32 cent. Comparing, 
the electrical generation actually costs 7.2 times as much as 
the other. This com^parison has dealt with the fuel costs at 
the plant and has not taken into account the depreciation, 
labor costs, etc., the object being to show relative efficien- 
cies only. 

Another way of looking at this subject is as follows. 
A fairly large turbo-generator set (say 500 K. W.) will 
deliver 1 kilo-watt hour to the switchboard on 20 pounds 
of steam. With 10 per cent, additional steam for auxiliary 
units, this amounts to 22 pounds of steam per kilo-watt hour 
at the switchboard. One pound of steam generated in a 
plant of this kind with the above efficiencies and value of 
coal, also with a steam pressure of 150 pounds and a good 
feed water heater, will give to each pound of steam approxi- 
mately 1000 B. t. u. This makes 22000 B. t. u. or 2.8 pound3 



282 



HEATING AND VENTILATIO^f 



of coal required to each kilo-watt output. This is about 10 
per cent, less than the above figures. 

The ratio of 7 to 1, as shown in the above efflciencies, 
does not seem to hold good in the selling price to the con- 
sumer In round numbers, district Steam and hot water 
heating systems supply 25000 B. t. u. to the consumer for 
one cent. The cost for electrical energy to the <=onsmi.er is 
between 6 and 7 cents per kilo-watt. This gives 3412 ^ 6.5 
= 525 B. t. u. for one cent. Comparing with the above, gives 
a ratio of 48 to 1. 

185. The Probable Future of Klecirical Heating:— Be- 
cause of the low efficiency of electrical heating as compared 
to other methods of heating, it is very probable that it will 
not replace the other methods except in so far as the con- 
veniences of the user is the principal thing sought for, and 
the expense of operating a minor consideration. In some 
forms of domestic service, however, electrical heating is 
sure to find considerable usefulness. The temperatures of 
low pressure steam and hot water, together with the incon- 
venience of use, are such as to eliminate them from many 
of the household economies. They will probably continue 
to be -used for house heating, water heating and laundry 
work For occupations that require temperatures above 2oO 
degrees, such as broiling, frying, ironing, etc.. the electrical 

supply will be in demand. , „/, 

Heating by electricity on a large scale is being planned 
m Stavanser, Norway. 25000 horse-power can be developed 
by water power. This will be turned into electrical energy 
and sold at $7.00 per horse-power year. 

REFEREXCBS. 
References on Electrical Heating. 

Technical Periodicals. 

and Steam Seating, Feb 1907 p.^«^ 26. The 

W. S. Hadaway Jr., ,^.^^- ^.g 4^0 ^ 9^^ and 1358, and 

^Tf^! p"^!,""^^! v" lai f\iorr37.^^K?icrrt^ 

ISBce-Nrr^elp^^^ 

ilec?rlc Bon"e^r!' June 20, ipio^ p. 1680^ CassierS Magazrne. 
Electric Heaters, H. M. Phillips, Dec. 1909. 



CHAPTER XVI. 



REFRIGERATION, 



DESCRIPTION OF SYSTEMS AND APPARATUS. 

186, General Divisions of the Subject: — The rapidly in- 
creasing- demand for the cold storage of food products, the 
production of artificial ice and the cooling of buildings have 
developed for the heating engineer a broad and inviting 
field, namely, refrigeration. A municipal electric or pump- 
ing station with a district heating plant to utilize the ex- 
haust steam in winter and a refrigeration plant to utilize 
the same in summer furnishes a unique opportunity for 
economic eng-ineering. One application of the above princi- 
ple where a 10-ton ice plant of the absorption type was so 
operated in a town of 3500 population and earned a dividend 
of 13 per cent, on the investment, is proof, if any is needed, 
that the field is an intensely practical one. 

As in heating- systems there must be sources of heat, 
circulating mediums, distributing systems and delivering 
systems whereby the carriers give up their heat at the 
proper places in the circuits, so in 'refrigerating systems 
there must be sources of minus heat or of heat abstraction, 
circulating mediums, distributing systems and receiving sys- 
tems whereby the carriers take up heat at the proper places 
in the circuits from articles or rooms that are being cooled. 
The carriers (circulating mediums), and the receiving and 
transmitting of the heat to and from them present no special 
difficulties or great diversity of practice, but in the methods 
of producing and maintaining the sources of minus heat 
there are considerable diffe-rences and numerous methods. 

187. Refrigerating Systems may be divided into two 
groups, those producing cold by more or less chemical action 
between ingredients upon mixing, called chemical systems, and 
those producing cold by the evaporation of a liquified gas 
or the expansion of a compressed gas, called mechanical sys- 
tems. Chemical systems are used only occasionally in com- 
mercial work, but are frequently found in small sized plants 
for domestic purposes. Low first cost and convenience of 
handling are the principal advantages. This division in- 
cludes the simple melting of ice and the mixing of ice and 



284 



HEATING AND VENTILATION 



salt for temperatures as low as to —5 degrees. The latter 
is much used in domestic processes for the production of 
table ices, etc. Other ingredients used in the mixtures with 
the corresponding temperature drops which may be ex- 
pected are given in Table 53, Appendix. The chemical 
method of producing cold is occasionally used to maintain 
low temperatures in storage rooms while repairs are being 
made upon the regular machinery. The chemical methods 
of cooling are so simple in principle that they will not be 
discussed further in this work. Mechanical systems include 
all the practical methods of commercial refrigeration. These 
are, the vacuum system, the cold air system, the compression system 
and the absorption system. 

188. Vacuum System: — This system was formerly of 

some importance but of late years has given place to other 
and more efficient methods. Fig. 129 shows a vacuum sys- 
tem in diagram. If a spray of water 
or brine is injected into a chamber 
that contains pans of sulphuric acid 
and is kept at a partial vacuum of 
one or two ounces, the acid absorbs 
the water vapor from the spray, thus 
assisting in maintaining the vacuum 
and lowering the temperature of the 
remainder of the spray. The vapor- 
ization of the part that is absorbed 
by the acid requires heat. This 
heat is taken from the liquid of the 
spray that is not absorbed, conse- 
quently the temperature of the re- 
maining liquid is lowered. In a 
system of this kind a temperature 
of 32 degrees may easily be ob- 
tained. The water or brine after 
cooling is then circulated through 
^i^- ^^^- the coils of the cold storage room 

where it takes up the heat of the rooms and contents and 
returns to the vacuum chamber to be ag^in partially evapo- 
rated and cooled. 

189. Cold Air System:— The cold air system Is used prin- 
cipally on ship board. Fig. 130 shows diagrammatically the 
parts and the operation of the system. The cycle has four 



VACUUM 
CHAM8ER 



-^ 



^ 



REFRIGERATION 



285 




Fig. 130. 



parts, compression In one of the cylinders of the compressor, 
cooling in the air cooler by giving off heat to the cold water 
thus removing the heat of compression, expansion in the sec- 
ond cylinder of the compressor thus cooling the air, and 
refrigeration in the^cold storage room where the heat lost dur- 
ing expansion is regained froin the articles in cold-storage. 
Cold air machines work at low efficiencies because of the 
necessarily large cylinders and their attendant losses due 
to clearance, heating of the compression cylinder, snow in 
the expansion cylinder and friction. The system has much 
to recommend it, however, since it is extremely simple, occu- 
pies a very small space compared with other systems and 
uses no costly gases, chemicals or supplies. 

190, The Compression and the Absorption Systems have 
in common this fact — both use a refrigerant, i. e., a liquid hav- 
ing a comparatively low boiling point. Perhaps the most 
common refrigerant is anhydrous ammonia, which boils, at 
atmospheric pressure, at 28.5 degrees below zero and in 
doing so absorbs as latent heat 573 B. t. u. Table 54, Ap- 
pendix, gives further properties. Other refrigerants used 
to a lesser extent are sulphur dioxide, SO2, which boils at 
—14 degrees under atmospheric pressure with a latent heat 



286 HEATING AND VENTILATION 

of 162 B. t. u. and carbon dioxide, CO2, which boils at — 30 
deg-rees under a pressure of 182 pounds per square inch 
absolute with a latent heat of 140 B. t. u. A comparison ot 
the temperatures and pressures of four common refriger- 
ants is given in Table 59, Appendix. Pictet's fluid is a mix- 
ture of 97 per cent, sulphur dioxide and 3 per cent, carbon 
dioxide. 

A choice of a universal refrigerant can scarcely be made 
because of the varying conditions of individual plants. The 
principal difficulty with the use of sulphur dioxide is the 
fact that any water uniting with it by leakage immediately 
produces sulphurous acid with its corroding action upon all 
the iron surfaces of the system. This same objection holds 
also for Pictet's fluid. The objections to the use of carbon 
dioxide are, first, its comparatively low latent heat, and 
second, the high pressure to which all parts of the apparatus 
and piping are subjected. Pressures of from 300 to 900 
pounds per square inch are very common. Perhaps the worst 
charge that can be made against ammonia as a refrigerant 
is that it is highly poisonous and corrodes metals, particu- 
larly copper and copper alloys. However, the high latent 
heat of ammonia, together with the fact that its pressure 
range is neither so high as with carbon dioxide, nor so low 
as with sulphur dioxide, are perhaps the chief reasons for 
the very general preference for ammonia as the comjuercial 
refrigerant in compression systems; while its great affinity 
for and isolubility in water, are what make the absorption 
isystem a possibility. 

191. Compression System: — Compression machines may 
work well with the use of any one of the four refrigerants of 
Table 59, df the proper pressures and temperatures are ob- 
served and maintained. The common refrigerant for this 
type is, however, anhydrous ammonia, for reasons given 
above. Fig. 131 shows a diagramimatic sketch of the com- 
pression system. To follow the closed cycle of the ammonia, 
start with a charge being compressed in the cylinder of the 
compressor. From this it is conveyed by pipe to the con- 
denser which, being cooled by water, abstracts the latent 
heat of the refrigerant and condenses it to a liquid. From 
the condenser the liquid refrigerant is conveyed to the ex- 
pansion valve through which it expands into the evaporator 
or brine cooler. In changing from a liquid to a gas in the 
evaporator it absorbs from the brine an amount of heat 



HEFRIGERATION 



28? 



REFRIGERATOR 
ROOn AT 50 




COOLING WATER LIQUID AHnONIA EXPANSION VALVE LIQUID AimONlA 

Fig. 131. 



WARn BRINE 



equivalent to the heat of vaporization of the ammonia. 
Upon leaving the evaporator the refrigerant is again ready 
for the cylinder of the compresso.r, thus completing the 
cycle. 

If the refrigerant is. ammonia, the compressor is com- 
monly of the vertical type, direct connected to a horizontal 
Corliss engine as shown in Fig. 132. This type of com- 




TEN TON AMMONIA COMPRESSOR 

Fig. 132. 



UNIVERSITY OF NEBRASKA 



pressor combines the high efficiency of the Corliss engine 
with the vertical type of compressor which is probably the 
best type for reliable service of valves and pistons. The 
vertical compressor is usually single acting with water 
jacketed cylinders. Horizontal compressors are usually 
double acting, as shown in Fig. 133, where the prime mover 



28S 



HEATING AND VENTILATION 




Fig. 133. 



is a direct connected electric motor. Poppet valves in this 
type are placed at an angle of 30 degrees to 45 degrees with 
the center line of the cylinder, a construction made neces- 
sary by space restrictions on the cylinder heads. Compres- 
sors for other refrigerants are commonly of these same 
types, the main difference being that compressors for carbon 
dioxide systems are nearly always two-stage to produce 
high compressions. The intermediate cooler pressures range 
from 300 to 600 pounds per square inch. Horizontal steam 




Fig. 134. 



REFRIGERATION 



289 



cylinders in -tandem with the compressor cylinders are com- 
mon for the carbon dioxide systems and the compressor cyl- 
inders are usually single acting". 

192. Condensers for Compression Systems are classi- 
fied under four heads, atmospheric condensers, concentric 
tube condensers, enclosed condensers and submerged conden- 
sers. An elevation of an atmospheric condenser is shown in 
Fig. 134. As illustrated it consists of vertical rows of pipes 
so connected by return bends as to make the hot refrigerant 
pass through each pipe beginning at the top, while the cold 
water main at the top of the row furnishes a spray of water 
which trickles over the outside of the pipes. The gas on 
the inside of the pipes is thus cooled by the extraction of 
the quantity of heat that is used in raising the temperature 
of the water and evaporating a part of it. The complete con- 
denser may consist of any required number of these vertical 
rows, placed side by side, each row properly connected to 
the hot gas header and to the liquid header. 

An elevation of one section of a concentric tube condenser is 
show^n in Fig. 135. The arrows show the paths of the gas 
and water. As in the atmospheric type the gas enters at the 
top and the liquid is drawn oft below. In its descent It 











uQW AmjNA 



290 



HEATING AND VENTILATION 



passes throug-h the annular space between the- two concen- 
tric pipes and is cooled by the atmosphere on the outside of 
the larger pipes and by the water circulating through the 
inner pipes. This condenser has the advantage over the sim- 
ple ^atmospheric condenser in that the water may be made to 
have an upward course throug^h the apparatus, thus bring- 
ing the coldest water in contact with the pipes carrying the 
liquid rather than with the pipes carrying the hot gas. 
Since the efficiency of the plant as a whole is very largely 
dependent upon the temperature of the liquid at the expan- 
sion valve this matter of the "counter flow" of the cooling 
water is an important one. Fo.r the medium sized and large 
compression systems this form of condenser is used almost 
without exception. 

The enclosed condenser. Fig. 136, is very similar to the sur- 
face coil condenser in steam engine 
plants. It consists -of a cylindrical 
chamber with a number of concen- 
tric pipe spirals connecting a hot 
water header at the top with a cold 
w^ater header at the bottom of the 
cylinder. The pipes of the spirals 
are provided with stuffing boxes 
where they pierce the upper and 
lower heads of the cylinder. With 
this condenser a counter flow of 
the water is used, the cold water en- 
tering the bottom of the coils and 
flowing upward, so that the liquid re- 
frigerant at the bottom of the cylin- 
der is very near the temperature of 
the incoming water. 

A submerged condenser, as the name 
implies, contemplates a rather large 
body of water below the surface of 
which there is submerge-d a coil for 
circulating the hot refrigerant. Fig. 
137 shows a section of such a con- 
denser. The hot gas enters at the 
top fitting of the coil and leaves at 
lower fitting. Cold water is constantly fiownng in at the bot- 
tom of the tank and leaving by the overflow at the top, being 
heated as it rises. The form of the coil is usually spiral, 




Fig. 136. 



REFRIGERATION 



291 



although this condenser may be built with coils of the re- 
turn bend type when larger surface is required. Only the 
smaller compression plants use the enclosed or the sub- 
merged type of condenser. 




Fig. 137. 

In general, condensers may be considered vital factors 
in the economy of compression plants. They must be reliable 
in service and economical in operation, and must be so de- 
signed and proportioned that they will deliver liquid re- 
frigerant within five degrees of the temperature of the in- 
coming cooling water. A condenser should present all 
joints, particularly those holding the refrigerant, to plain 
view for easy inspection and repair. Since it is the func- 
tion of the condenser to dissipate the heat of the refrigerant 
gas, it is not- uncommon to install it upon the roof or out- 
side the building in some cool place. This is especially true 
where the atmospheric or the concentric tube types are 
used. In such positions the heat radiated by the condenser 
is not given back to the rooms and piping systems. In addi- 
tion, the cooling action of the atmosphere 'assists in making" 
the system more efficient. 



292 



HEATING AND VENTILATION 



193. Evaporators for compression systems may be con- 
sidered as condensers, reversed in action but very similar 
in form. If the refrigerating effect is accomplished by the 
brine cooling system an evaporator of some type will be 
necessary, but if the refrigeration is accomplished by circu- 
lating the expanding refrigerant itself, no evaporator is re- 
quired. Evaporators, or brine coolers, may be classified 
according to the method of construction, as shell coolers and 
concentric tube coolers. 

The shell cooler takes various forms. One is shown by 
Fig. 136, being in effect an enclosed condenser with brine 
instead 'Of cold water circulating in the coils. The heat of 
the brine is transferred to the cool liquid refrigerant, caus- 
ing the refrigerant to evaporate and take from the brine 
an amount of heat equal to the latent heat of the refriger- 
ant. The proper height to which the liquid refrigerant 
should be allowed to rise in the evaporator is a very much 
disputed point, some 'Old and experienced operators claim- 
ing greatest efficiency when about one-third of the cooling 
surface is covered with liquid refrigerant leaving two- 
thirds to be covered with gaseous refrigerant. Others claim 
that the entire surface should be covered or "flooded" with 
liquid refrigerant. These points of view give rise to 
the two terms dry systems and flooded systems. Of late years 
the flooded systems are gaining somewhat in favor, a sepa- 
rator being installed between the evaporator and the com- 
pressor to prevent any liquid being drawn into the com- 
pressor cylinder. This separator drains any liquid which 




Fig. 138. 



REFRIGERATION 293 

may collect therein, back into the evaporator. In the flooded 
system the brine cooler more commonly takes the form 
shown in Fig. 138, where at the end A D of. the brine tank 
ABCD is shown the flooded cooler E. This cooler consists 
of a boiler shell filled wuth tubes, the brine circulating 
through the inside of the tubes while the interior of the 
large shell is nearly or quite filled with liquid refrigerant. 

Concentric tuhe 'brine coolers are made of piping very similar 
in principle to that shown in Fig. 135, with the exception 
that instead of two concentric pipes, three are more com- 
monly employed. The brine circulates through the inner- 
most of the three and through the outermost, while the 
annular space between the smallest pipe and the middle 
pipe is traversed by the liquid refrigerant. In this way 
the annular space filled with refrigerant has brine on both 
sides and the cooling of the brine is very rapid. The numer- 
ous joints in this cooler present a constant source of trouble. 
Salt brine will usually freeze in the inner pipe, so that cal- 
cium chloride brine must be used. 

A choice of evaporators or coolers depends mainly upon 
"Whether the plant is to run continuously or intermittently. 
When run continuously only a small amount of brine is 
required and this, when cooled quickly and circulated 
quickly, would call for a concentric tube cooler. When run 
intermittently a much larger body of brine is desirable so 
as to remain cool longer during the night hours when the 
plant is not operating. For this condition a shell type 
cooler would probably be preferred. 

In addition to the condensers and evaporators that were 
described in detail, there are to be found on the well equip- 
ped compression system the following pieces of apparatus 
which will be mentioned and described only briefly. An oil 
separator is commonly found in the line connecting the con- 
denser with the compressor. This is simply a large cast 
iron cylinder with baffle plates to separate the oil from the 
ammonia. Since the oil is heavier than the ammonia it set- 
tles to the bottom and may be drawn off. An ammonia scale 
strainer is often found just before the compressor intake. 
Small purge valves are located at all high points in the 
system for the purpose of exhausting the foul gases or the 
air which may collect in the system. Such a purge con- 
nection is shown on the right end of the upper coil in 
Fig. 134. 



294 



HEATING AND VENTILATION 



194. Pipes, Valves and Fittings for compressor refrig-er- 
ant piping- are considerably different from the standard types. 
If the refrigerant is ammonia, no brass enters into the de- 
sign of any part of the piping or auxiliaries traversed by the 
ammonia. The operating principles of all valves are the 
same as standard ones but they are made heavier and en- 
tirely of iron, or iron and aluminum. The common threaded 
joint used on all .standard fittings is replaced in ammonia 
systems by the bolted and packed joint. It is not within the 
scope of this work to go into these details further than to 




Fig. 139. Fig. 140. 

give a section of an ammonia expansion valve, Fig. 139, and 
a section of a typical ammonia joint, Fig. 140. 

195. Absorption System: — As stated in Art. 190, the 
great affinity of ammonia gas for water and its solubility 
therein, are what make the absorption system a possibility 
and give it the name as well. At atmospheric pressure and 
50 degrees temperature one volume of water will absorb 
about 900 volumes of ammonia gas. At atmospheric pres- 
sure and 100 degrees temperature one volume of water 
will absorb only about one-half as much gas, or 450 vol- 
umes. If then, one volume of water is saturated at 50 de- 
grees with ammonia gas and heated to 100 degrees there 
Will be liberated about 450 volumes of ammonia gas. Hence 
it is evident that a stream of water may be used as a con^ 
veyor of ammonia gas from one place or condition to an- 
other, say from a condition of low temperature and pres- 
sure where the absorbing stream of water would be cool, to 



REFRIGERATION 



295 



a condition of high temperature and pressure, where the 
g-as would be liberated by simply heating the water. It will 
be noticed that the gas has been transferred as a liquid 
without a compressor or any compressive action, by pump- 
ing a stream of water of approximately one-four hundred 
and fiftieth of the volume of the gas transferred. This, in 
the abstract, is the method employed in the absorption 
system to convey the ammonia gas from the relatively low 
temperature and pressure of the evaporator to the high 
temperature and pressure at the entrance of the condenser. 
The absorption system, when closely compared in prin- 
ciples of operation to the compression system, differs only 
in one respect, namely, the absorption system replaces the 
gas compressor by the strong and weak liquo<r cycle. As 



^^^^'^'l^^'^^^. 




Fig. 141. 



shown in Fig. 141, both sys- 
tems have arrangements of 
condenser, expansion valve 
and evaporator that are iden- 
tical, hence the part of the 
cycle through these need not 
be considered. The problem 
of completing the cycle from 
evaporator t o condenser, 
however, is solved- quite dif- 
ferently in the two systems. 
In the compression system 
(upper diagram) the evapo- 
rator delivers the expanded 
gas to the compres- 
sor, from which, 
under high pres- 
sure and tempera- 
ture, it is delivered 
to the condenser 
and the cycle is 
completed. In the 
absorption system 
(lower diagram) 
the evaporator de- 
livers the expanded 
gas to an absorber, 
in which the gas 
comes in contact 
with a spray of so- 
called weak liquor, 



296 HEATING AND VENTILATION 

consisting of water containing about 15 to 20 per 
cent, of anhydrous ammonia. The weak liquor absorbs 
the ammonia gas through which the liquor is sprayed and col- 
lects in the upper part of the absorber as strong liquor, contain- 
ing about twice as much anhydrous ammonia as the weak 
liquor, or 30 to 35 per cent. From here it is pumped through the 
exchanger (which will be ignored for the present) into the 
generator at a pressure of about 170 pounds per square inch 
gage. In the generator heat is supplied by steam coils im- 
mersed in the strong liquor. As this liquor is heated it 
gives up about half of the contained ammonia gas which 
rises and passes from the generator to the condenser, thus 
completing the ammonia or primary cycle, while the weak 
liquor flows from the bottom of the generator through the 
exchanger and pressure reducing valve back to the ab- 
sorber, thus completing the secondary or liquor cycle. 

In general then, the absorption system uses two cycles, 
that of the ammonia and that of the liquor, the paths of the 
two cycles being coincident from the absorber to the gen- 
erator. The liquor pump serves to keep both cycles in mo- 
tion. The pump creates the pressure for both cycles and 
the expansion valve and the reducing valve reduce the 
pressure respectively for the ammonia cycle and the liquor 
cycle. The exchanger does not mix or alter the condition of 
the two streams of liquor passing through it, for its only 
function is to bring these two streams close enough that 
the heat of the weak liquor from the generator may be trans- 
ferred to the strong liquor going to the generator. Stated in 
other words, the exchanger heats the strong liquor by cool- 
ing the weak liquor, thus effecting a saving of heat which 
would otherwise be lost, since the weak liquor must be 
cooled before it is ready to properly absorb the gas in the 
absorber. 

196. An Elevation of an Absorption System with the 
elements piped according to what is considered best prac- 
tice is shown in Fig. 142. Starting at the expansion valve, 
the ammonia (liquid, gas or gas in solution) passes in order 
through these pieces of apparatus: the evaporator, the ab- 
sorber, the liquor pump, the chamber of the exchanger or the 
coil of the rectifier, the generator, the chamber of the recti- 
fler and the condenser back to the expansion valve. At the 
same time the liquor used to absorb the gas travels in order 
through these pieces: the absorber, the liquor pump, the 



REFRIGERATION 



297 



COLD BRINE TO REFREERATQR 
ROOM 




COOUNG WATER 
TO ABSORBER 



Fig. 142. 



chamber of the exchanger or the coil of the rectifier, the 
generator, the pressure reducing valve and the coil of the 
exchanger back to the absorber. The method of pipe connec- 
tions shown is a very common one although some varia- 
tion may be found, especially in the continued use of cool- 
ing water in consecutive pieces of apparatus. As shown, 
the cooling water is first used in the condenser. This will 
be found so in all plants. From the condenser the cooling 
water may next be taken to the absorber, as shown in the 
sketch, or it may be used in the rectifier coil instead of the 
strong liquor. In recent years the practice of by-passing 
a certain amount of the cool, strong liquor from the pump 
through the rectifier is gaining in favor. Fig. 142 shows 
a plant having bent coil construction. Plants are also built 
having straight pipe construction, where all coil surfaces 
shown are replaced by straight pipes, the condenser being 
usually of the concentric tube atmospheric type and the 
evaporator being also of the concentric tube brine cooler 
type, as mentioned under compression systems. Both types 
of absorption plants are found in use. 



298 



HEATING AND VENTILATION 



197. Generators are classified as horizontal and verti- 
cal. Fig. 143 shows a horizontal type generator, with the 



J^ 



a=^ms&iit =:^ "I , 




Fig. 143. 

analyzer and exchanger, and Fig. 144 shows the vertical 
type, also with the analyzer. The horizontal type may have 
one or more horiontal cylinders equipped with steam codls. 
The analyzer, which may be considered as an enlarged dome 
of the generator, is used to condense the water vapor which 
rises from the surface of the liquid in the generator. To 
do this the analyzer has a series of horizontal bafCle plates 
through which the incoming cool, sitrong liquor trickles 
downward while the heated mixture of ammonia gas and 
water vapor passes upward through interstices. In this 
way the strong liquor gradually cools the ascending water 
vapor and condenses much of it on the surfaces of the 
baffle plates. 

198. Rectifiers are arrangements of cooling surface 
designed to thoroughly dry the gas just before it p-asses 
into the condenser. This is accomplished by presenting 
to the hot product of the generator just enough cooling sur- 
face to condense the water vapor without condensing any of 



REFRIGERATION 



299 





Fig-. 144. 



the ammonia gas. Rectifiers are 
very similar in general design to 
the various types of condensers, 
there being atmospheric, concen- 
tric tube, enclosed and submerged 
rectifiers just as the.re are these 
same type of condensers, each de- 
scribed under the head of con- 
densers for compression systems. 
Rectifiers may save hea^t by the 
arrangement shown in Fig. 142, 
where the heat abstracted from the 
water vapor is given to the cool, 
strong liquor before entering the 
generator. As shown, the strong 
liquor may be divided, part pass- 
ing through the rectifier and part 
through the exchanger, or the 
strong liquor may all go through 
the exchanger first and then 
through the rectifier. Where 
strong liquor is so used, the recti- 
fier is always of the enclosed 
type. Reotifiers using water as 
the cooling medium are often 
called dehydrators, the term rec- 
tifier being more properly used 
when the cooling medium is the 
strong liquor. 

199. Condensers for absorption 
systems do not differ in design 
from those used for compression 
systems. The same types are used, 
and in the same manner, the sur- 
face being somewhat less due to 
the precooling effect of the recti- 
fiers or dehydrators. As a gen- 
eral statement, it is claimed that 
from 20 to 25 per cent less surface 
is required in the condenser for an 
absorption machine than is re- 
quired in one for a compression 
machine. 



300 



HEATING AND VENTILATION 



WEAKLlQUOra 




///// iWo. 

/SPRAY/ / ;^i \PUTC\\ 



ooooo(^3hrDooooo 
ooooo^ =^00000 
oooooc^ ^pooooo ^^^ 
OOOOOO^H r^ooooo I 



Fiff. 145. 



200. Absorbers may be classified as dry absorbers, wet 
absorbers, atmospheric absorbers, concentric tube absorb- 
ers and horizontal and vertical tubular absorbers. In the 
dry absorUr, the top section of which is shown in Fig. 145, 

the weak liquor enters at the 
middle of the top header and 
is sprayed upon a spray pan, 
from which it drips downward 
over the coils. The gas enters 
as shown, part being delivered 
above the spray plate, so as to 
come into contact with the 
spray and the larger part being 
taken downward through the 
central pipe to a point near the 
bottom of the absorber, from 
which point it flows upward 
against the descending weak liquor by which it is absorbed. 
As the gas is dissolved by the weak liquor the heat of ab- 
sorption is given off, and taken up by the cooling water in 
the coils. The result is a strong liquor which collects in 
the absorber ready to be delivered to the pump. 

The wet al)sorher, on the contrary, has practically the 
whole body filled with weak liquor and the ammonia gas 
enters near the bottom, bubbling up through the weak 
liquor thus saturating it. Various baffle -plates with fine 
perforations break up the gas into small bubbles thus aid- 
ing in presenting a large surface of gas to the liquor 
which, as it becomes saturated and lighter, rises to the top 
of the body of the absorber and is ready to be drawn off by 
the pump. Instead of spiral cooling coils, this type is often 
made with straight cooling tubes inserted between two tube 
sheets, boiler fashion. This straight tube construction is 
much simpler and cheaper, and much more easily cleaned 
than the spiral type. It is favored by some on this account, 
especially where the cooling water has a tendency to form 
scale. 

Atmospheric absorlers resemble atmospheric condensers of 
the single tube type. The ammonia gas and weak liquor en- 
ter the bottom through a fitting commonly called a mixer, 
and the two flow upward through the inside of the pipe 
while the cooling water is in contact with the outside thus 
taking up the heat of absorption generated within the pipes. 



REFRIGERATION 301 

Concentric tude absorbers are very similar in design to con- 
centric tube condensers, the cooling- water passing through 
the central tube and the weak liquor and expanded gas en- 
tering at the bottom of the annular space and circulating to 
the top, absorption taking place on the way. Because of the 
small capacity of the last two mentioned absorbers, it is 
necessary to use with them an aqua ammonia receiver be- 
tween the absorber and the ammonia pump, to act as a 
reservoir for storing a reserve supply of the strong liquor. 

Horizontal and vertical tubular absorbers are those in which 
the cooling surface is composed of straight, horizontal or 
vertical tubes inserted between tube sheets, the cooling 
water flowing inside the tubes and the absorption taking 
place within the drum or body of the absorber. 

201. Excliangers may be of two types, the shell type 
or the concentric tube type. The shell type, as the name im- 
plies, is composed of a main body or shell through which 
circulates the strong liquor to be heated and within this 
shell is a coil or other arrangement of heating pipes through 
which the hot, weak liquor flows. Fig. 142 shows the ele- 
mentary arrangement of such an exchanger. Concentric 
tube exchangers are used on large plants. They are similar 
in every way to the concentric tube condensers shown in 
Fig. 135, with the exception that larger pipes are needed 
for the exchangers. The cold, strong liquor is usually car- 
ried through the pipes and the hot, weak liquor through the 
annular space. The great advantage of this type of ex- 
changer is the same as that of the concentric tube con- 
denser, namely, the counter flow of the two streams. With 
this arrangement the total transfer of heat is a maximum, 
for which reason this tj^pe of exchanger is generally pre- 
ferred. 

202. Coolers for the weak liquor are often found in 
plants. This piece of apparatus is not indicated in Fig. 142. 
It is usually installed as the lower three coils of the atmos- 
pheric condenser, and hence is simply a small condenser 
used to further cool the weak liquor just before its entrance 
into the absorber. With a counter flow, concentric tube ex- 
changer a weak liquor cooler is seldom found necessary. 

203. The Pump used in absorption sj^stems to raise the 
pressure of the strong aqua ammonia may be steam driven, 
electric driven or belt driven, as best suits the particular 

plant conditions. The power required by this piece of appa 



202 HEATING AND VENTILATION 

ratus is about one horse power per 20 to 25 tons of refriger- 
ation capacity. 

204. Compression Systems and Absorption Systems Com- 
pared: — A comparison drawn between the compression sys- 
tem and the absorption system brings out the following 
facts. The compression system depends fundamentally upon 
the transferring of heat energy into mechanical energy and 
vice versa, with the attendant heavy losses. The absorption 
system merely transfers heat from one liquid to another. 
This is a process which is attended by only moderate losses. 
The compression system is comparatively simple, its pro- 
cesses readily understood and its machinery easily kept in 
good running order. The absorption system is complicated 
with a greater number of parts, its processes are often not 
thoroughly understood by those in charge and its machinery 
is likely to become inefficient because heat transferring sur- 
faces are allowed to become dirty. For these reasons the 
attendance necessary upon an absorption plant must be of a 
higher order than that necessary for a compression plant. 

205. Circulating Systems: — The refrigerating effect pro- 
duced by either one of the two systems may be delivered to 
the place of application in two ways. The first is the hrine 
circulation method wherein a brine cooler is used through 
which the brine flows causing the evaporation of the liquid 
refrigerant and the cooling of the brine. This cold brine is 
then circulated through pipes to the place where refrigera- 
tion is desired. Fig. 138 shows an evaporator placed in one 
end of a large brine tank. The refrigerating effect is car- 
ried to the cans of water by the circulation of this body of 
brine through the evaporator and out past the cans, the cir- 
culation through the channels shown being maintained by 
the pump. Brine, commonly used for such work, is made by 
dissolving calcium chloride in water. A 20 per cent, solu- 
tion is generally used. Salt brine is used to some extent 
but it has many disadvantages compared with calcium brine. 
The second method is the direct circulation method wherein the 
liquid refrigerant is conveyed to the place to be cooled, is 
passed through an expansion valve and then circulated 
through coils in the space to be refrigerated, changing into 
gaseous form as fast as it can absorb enough heat. If 
ammonia is the refrigerant the direct circulation is not often 
favored because of its highly penetrative nature and odor, 
even a leak so small as to escape detection being sufficient 



REFRIGERATION 



303 



to fill 'the refrigerated space witli tlie odor, wliich many 
food stuffs will absorb. 

206. There are Three Methods Employed for Maintain- 
ing Liow Temperatures in storage and other rooms. The 
first is by direct radiation where the pipes are placed within 
the room and the refrigerant is circulated through them. 
This is the oldest, simplest and. cheapest system to install. 
In this the proper location and arrangement of the pipes are 
essential to the most efficient operation. Since the tempera- 
ture to be maintained in a storage room depends upon the 
products to be kept in the room, it may be necessary to have 
a considerable range of temperature. It is desirable to have 
the pipes arranged as coils in two or three sets, each being 
valved so that the amount of refrigerant being circulated 
may be increased or decreased as the temperature of the 
stored product may require. 

The pipes should be set out from the wall several inches 
to give free air circulation and keep the frost that collects 
on them from coming into contact with the wall. The coils 
should be so placed that the temperature of all parts of the 
room may be kept as nearly uniform as possible. Some 
products keep as well in still air as when it is in motion, but 
others, such as fruits, eggs, cheese, etc. are better pre- 
served when the air is circulated. Circulation may be ef- 
fected in a room piped for direct radiation by putting aprons 
over the coils as shown in Fig. 146. These aprons consist of 

12 inch boards D nailed to 
studding E and the whole 
fastened to the coils, the 
studding serving to keep the 
boards from coming into 
contact with the pipe coils. 
A false ceiling F is placed a 
few inches below the ceiling 
of the room so that the 
warm air flows towards the 
pipes and over them, drop- 
ping to the floor and passing 
out under the lower edge of 
the apron into the room. 
Wherever direct radiation is 
used drip pans s-hould be 
placed directly underneath the coils in order to catch and 
drain off the water when the coils are cut out and the frost 



y/^/y////y/////j//////////////////x 



Fig. 14 



304 



HEATING AND VENTILATION 



yMm^//my(m////// ////m 



k 






kl 



k 



^ * 

r 



4 




'^ 



tJ4 



melts. This water should be drained into a receptacle that 
can be easily emptied when filled. 

The second method of room cooling is by indirect radiation. 
Let Fig. 147 represent a section of a storage building. The 
essential parts of the cooling system are, 
a bunker room AC, in the top part of the 
building, containing the cooling coils 
By a series of ducts on either side of the 
building, so arranged that the air after 
passing over the cooling coils, drops 
downward. These ducts are provided 
with dampers for admitting as much of 
the cold air to the rooms as is desired. 
On becoming warmed this air is crowded 
out on the opposite side of the room into 
the ducts K and rises to the bunker- 
room where it is again cooled by passing 
over the coils. By the use of the damp- 
ers the cold air may be cut off from any 
room or admitted in large quantities 
thus making it an easy matter to main- 
tain the temperature at any point de- 
sired. The ducts leading the air from 
the rooms should be 25 per cent, larger 
than the ones leading to the rooms and 
the latter should have about three square 
inches cross-section per square foot of 
floor area in rooms having a ten foot 
ceiling. 

The third method is by means of a 
plenum system of air circulation, Fig. 148. The arrangements 
are quite similar to those of the plenum system for heating, 

except that the heating coils 
are replaced by the refrigerat- 
ing coils. The air required for 
ventilation is blown over the 
coil surface, erected in a coil 
or bunker room, over which, 
oftentimes, cold water is 
sprayed. This not only washes 
the air but tends to lower its 
temperature. If ammonia is 
used as a refrigerant, brine is 
circulated in the coils, but if 



Fig. 147. 




Fig. 148, 



REFRIGERATION 305 

carbon dioxide is used direct expansiion is employed, thus 
dispensing with the use of brine. The principal advantage 
of the plenum system of cooling is that a positive circulation 
of air may be maintained in any room even though the 
bunker room be placed on the first floor or in the basetment 
of the building. This is the system used in large buildings 
that are cooled during the summer as well as heated dur- 
ing winter, in factories where changes of temperature seri- 
ously affect the product, as in chocolate factories, in fur 
storage rooms, in drying the air before it is blown into blast 
furnaces and in the solution of many other important eco- 
nomic problems. 

207. Influence of tlie Dew Point: — In cooling a building 
by means of a plenum refrigerating system, great trouble 
is experienced with the formation of ice on the coils. For 
example, suppose such a cooling system on a hot summer 
day is taking in air at 90 degrees temperature and 85 per 
cent, humidity. If this air is cooled only ten degrees (see 
chart, page 29), it will have reached its dew point and as 
the cooling continues will deposit frost and ice on the coils 
from the liberated modsture, the air meantime remaining at 
the saturation point and being so delivered to the rooms. The 
undesirable feature of delivering saturated air to the rooms 
may be avoided by cooling only part, say half of the air 
stream, considerably lower than the final temperature de- 
sired, and then mixing it with the other half, which is 
drier, before delivering it to the rooms. The troublesome 
coating of ice and frost on the pipes may be avoided by 
combining the cooling system with the air washing system 
and using a brine spray instead of water for washing the 
air during cooling. The brine, which freezes at a very low 
temperature compared with water, plays over the cooling 
coils, and cleans both coils and air. The brine should pref- 
erably be a chloride brine. A modification of this method of 
avoiding ice and frost is to provide pans above the coils 
and fill them with lumps of calcium chloride. The pans 
have perforations so arranged that as the strong chloride 
solution forms (due to the deliquescence of the salt) it 
trickles down over the pipes and holds the freezing point 
of any collecting moisture far below the temperature of the 
coils. A sketch of this arrangement is shown in Fig. 149, 
which has the disadvantage of the clumsy handling of the 
calcium chloride. Plants operating only during the day, as for 



306 



HEATING AND VENTILATION 




Fig. 149. 



instance, auditoriums, commerce chambers, etc., often have 
no equipment for preventing the accumulation of frost and 
ice, it being allowed to form during the short period of use 
and to melt during the period of rest. 

208. Pipe Line Refrigeration: — In a number of the 
larger cities refrigeration is furnished to such places as 
cold storage rooms, restaurants, hotels, auditoriums, etc., 
by a conduit system or central station system. The length 
of the mains in the various cities where used, ranges from 
a few hundred feet to twenty miles and the circulating 
medium employed is either liquid ammonia or brine. In the 
ammonia system two pipes are used, one carrying the liquid 
ammonia to the place desired and the other returning it 
after expansion to the central station. When brine is used 
it is good practice to circulate it at from 12 to 15 degrees P. 
Occasionally the conduits carry three parallel pipes, two of 
which are for circulating the brine and the third is for 
emergency cases. The line should be divided into sections, 
with valves and by-passes so arranged that a defective sec- 
tion could be repaired without interfering with the other 
parts. All valves should be readily accessible and all high 
points in the system should be equipped with purge valves. 



REFRIGERATION 



307 



m 



The service pipes should be two inches in diameter and 
well insulated. 

Either the ammonia absorption or compression system 
may be used for cooling* the brine but according to Mr. Jos. 
H. Hart, the latter, making use of direct expansion, is the 
most efficient and the one most commonly installed. The 
loss by radiation to the pipes in the conduits is not great but 
numerous mechanical difficulties are yet to be overcome. It 
would seem desirable to make the pipe-line system of cool- 
ing general for residence use but as yet it has not been 

found economical to cool build- 
ings using less than the 
equivalent of 500 pounds of re- 
;^ni5i frigeration in 24 hours. Al- 
though not an efficient method, 
it seems probable that cold air 
refrigeration by using balanced 
expansion may supersede the 
other systems. 

209. As a Final Application 
of refrigeration we may men- 
tion the cooling of the drinking 
water supply in large office 
buildings, hotels, etc. Usually 
this is simply a small part of 
the work of a large refrigerat- 
ing plant. Fig. 150 gives a dia- 
grammatic elevation of such an 
arrangement. 
Fig. 150. 




7& 




CHAPTER XVII. 



REFRIGERATION CALCULATIONS. 



210. Unit 3Ieasurement of Refrigeration: — Since thft 
first efforts toward refrigeration employed the simple pro- 
cess of melting" ice by the abstraction of heat from nearby 
articles, it is not surprising to find the accepted standard 
unit for expressing refrigeration capacities referred to the 
refrigerating effect of a known quantity of ice. In fact, 
since the latent heat of fusion of ice is a constant, this 
furnishes an excellent basis for estimating refrigeration. 
The generally accepted unit of measure is the ton of refrigera- 
tion, which may be defined as the amount of heat (B. t. u.) which 
one ton of 2000 pounds of ice at 32 degrees, will al)sorh in melting to 
water at 32 degrees. Since the latent heat of ice is 144 B. t. u. 
per pound, one ton of refrigeration is equal to 288000 B. t. u. 
Just as a pumping plant is rated at a certain number of 
millions of gallons, meaning millions of gallons in twenty- 
four hours, so a refrigeration plant is rated in so many 
tons of refrigeration, meaning so many tons in twenty-four 
hours. Hence one ton of refrigeration capacity for one day 
is equivalent to 12000 B. t. u. per hour, this value being the 
unit of refrigerating capacity, sometimes referred to as tonnage 
capacity, or refrigerating effect, and usually designated by T. 

211. Calculation of Required Capacity: — To estimate 
closely the tonnage capacity of a refrigerating plant for 
any certain store space requires specific attention to supply- 
ing the following losses: 

(a) The radiated and conducted heat entering the 
room. This may be divided into that due to the walls and 
that due to the windows and sky-lights. 

(b) The heat entering by the renewal of the air, or 
ventilation of the enclosed space. This may be divided into 
heat given off by the air and heat given off due to the 
latent heat of the moisture. 

(c) The heat entering by the opening of doors. 

(d) The heat from the men at work, lights, chemical 
fermentation processes, etc. 

(e) The heat abstracted from material in cold storage. 
Refrigeration losses due to entrance of radiated and con- 
ducted heat may be calculated by formulas 10, 11 and 12, 



REFRIGERATION 



309 



Chapter III, if the proper transmission constants are in- 
serted. To obtain these constants for various types of in- 
sulation use Tables IV and XXIX. 



TABLE XXIX. 
Heat Transmission of Standard Types of Dry Insulation. 



Material 


K 


Material 


K 


Mill shaving-s, Type (a) 


Hair Felt, Type (a) 




1" thickness 


.1330 


1" thickness 


.138 


2" 




.1090 


1/4", %". U", Type (c) 


.105 


o' 




.0920 


Sheet Cork, Type (d) 




4" 




.0800 


4" with 1" air space 


.050 


5" 




.0710 


5" with 1" air space 


.037 


6" 




.0630 


3", Type (b) 


.087 


7" 




.0570 


r\ Type (a) 


.137 


8„ 




.0520 


Granulated Cork 




10" 




.0440 


4", Type (a) 


.071 


12'' 




.0390 


Mineral Wool 




14" 




.0340 


2%", Type (b) 


.151 


16" 




.0308 


1", Type (b) 


.192 


18" 




.0279 


Air Spaces 




20" 




.0255 


8", Type (a) 


.112 


22- 


* 


.0235 






24" 





.0218 







TAR PAPER 

SHAVING 53 




TAR R^PLR^ 




In g-eneral any space to be kept at or below zero degrees 
should have insulation allowing- no greater transmission 
than .04, and for spaces to be kept at from degrees to 30 



310 HEATING AND VENTILATION 

degrees no greater transmission should be allowed than .06, 
while for temperatures above 30 degrees a transmission as 
great as .1 is allowable. In any case, however, it should be 
remembered that the heat loss, and therefore the expense of 
operation, is directly proportional to this factor and the 
best possible insulation, consistent with available building" 
funds, is the one to use, the ceiling and floor being as care- 
fully insulated as the walls. Window construction should 
be tig-ht, non-opening, and at least double. 

The refrigeration Joss due to ventilation may be considered 
under two heads, i. e., the cooling of the air from the 
higher to the lower temperature, and the cooling, condens- 
ing and freezing of the moisture in the air. In this par- 
ticular, air cooling cannot be considered exactly the re- 
verse of air warming. In air warming the vapor present 
absorbs heat but this vapor has so little heat capacity com- 
pared with that of the air that no noteworthy error is intro- 
duced by ignoring the vapor. However, in air cooling the 
dew point is almost invariably reached and passed, so that 
considerable moisture is changed from the vapor to the 
liquid with a liberation of its heat of vaporization. This is 
considerable and cannot be ignored without serious error. 
If, further, conditions are such that this moisture is frozen, 
its latent heat of freezing must also be accounted for. 
These two items are relatively so large that to cool air 
through a given range of temperature may involve several 
times the heat transfer required to warm the same air 
through the same range of temperature. 

Application. — Assume outside air 95 degrees, relative 
humidity 85 per cent., temperature of air upon leaving cool- 
ing coils 30 degrees and temperature of coil surface 10 de- 
grees. If 180000 cubic feet of air per hour are drawn in 
from the atmosphere, the refrigerating capacity of the coils 
may be obtained as follows. To cool the air from 95 degrees 
to 30 degrees will require (formula 9), 

180000 X (95 — 30) 
= 212700 B. t. u. 



oa 



At 95 degrees and 85 per cent, humidity one cubic foot of 
air contains, (Table 10, Appendix,) .85 X 17.124 = 14.555 
grains of moisture. At 30 degrees and saturation one cubic 



REFRIGERATION. 311 

foot of air contains, (Table 10), 1.935 grains. Hence there 

180000 (14.555 — 1.935) 



would be deposited upon the coils — = 

7000 

324.5 pounds of moisture per hour. Now there would be 

absorbed from each pound of this moisture 

32 B. t. u. to cool from 95 to 32 degrees. 

1073 B. t. u. to change to liquid form. 

144 B. t. u. to freeze (if allowed to freeze on coils). 

11 B. t. u. to cool from 32 to 10 degrees. 



1260 B. t. u. total. 

Hence the coils would have to absorb from the moisture 
alone, 1260 X 324.5 = 408870 B. t. u. per hour, or for both 
moisture and air, 212700 + 408870 = 621600 B. t. u. per hour. 
This indicates, for the ventilation proposed, a tonnage capac- 
ity of 621600 -=- 12000 = 51.8 tons of refrigeration needed at 
the bunker room coilst The above provides that the air is 
rejected at the interior temperature, 30 degrees. Modern 
plants, however, would pre-cool the incoming air before it 
reached the bunker room by having part of its heat ab- 
sorbed by the outgoing 30 degree air, which would reduce 
the estimate somewhat below 51.8 tons. 

In considering the refrigeration loss due to the opening of 
doors no rational method of calculation is applicable, but if 
the nature of the cold storage service is such that doors are 
frequently opened, as high as 25 per cent, may be allowed. 
Generally this is taken from 10 to 15 per cent. 

The refrigeration loss due to persons, liglits, etc., may be 
estimated as suggested in Art. 31. If the cooling air is 
recirculated, the cooling" and freezing of the moisture given 
off by each person should be taken into account, especially 
if the number is large. For this purpose it is safe to assume 
a maximum of 500 grains of moisture given off per person 
per hour when such persons are not engaged in active phy- 
sical exercise. 

212. Calculations for Square Feet of Cooling Coil: — This 
problem presents greater uncertainty in its solution than 
does the design of a heating coil surface because of the lack 
of experimental data and because of the variable insulat- 
ing effect of ice and frost accumulations, if allowed to form. 
Professor Hanz Lorenz in "Modern Refrigerating Machin- 
ery," page 349, quotes 4 B, t. u. per square foot per hour per 



312 HEATING AND VENTILATION 

degree difference between the average temperatures on the 
inside and outside of the coils, as a safe designing value 
when the air speed is 1000 feet per minute over the coils. 
This is for plants in continuous operation, as abattoirs, cold 
stores and in places w^here no provision is made against ice 
formation. For clean pipe surface in the plenum air cooling 
plant of the New York Stock Exchange Building the heat 
transmission is approximately 430 B. t. u. per square foot 
per hour with air over coils at 1000 feet per minute. Under 
the average temperatures there used, this corresponds to a 
transmission per degree difference per square fooft per hour 
of approximately 7 B. t. u. These two values, 4 and 7, may 
be taken as about the minimum and maximum transmission 
constants for plenum cooling coil installations. 

For direct cooling coils, where the pipe surface is sim- 
ply exposed to the air of the room to be cooled, Lorenz 
recommends a transmission allowance of nat over 30 B. t. u. 
per square foot per hour, for in such installations the re- 
moval of ice and frost is seldom contemplated. For an aver- 
age room temperature of 30 degrees and average brine tem- 
perature of 10 degrees, this would correspond to 30 -^ 20 = 
1.5 B. t. u. transmitted per square foot per hour per degree 
difference. 

Applicatiox 1. — How many lineal feet of IV^ inch direct 
refrigerating coils would be required to keep a cold stor- 
age room at 30 degrees if the refrigeration loss ds 80000 
B. t. u. per hour total and the temperatures of the brine en- 
tering and leaving the coils are 10 degrees and 20 degrees 
respectively? Average brine temperature = 15 degrees. Al- 
lowing a transmission constant of 1.5, formula 30 becomes, 

H 

Rr — = — .0445 H 

1.5 (15 — 30) 

For this problem we have .0445 X 80000 = 3500 square feet, 
or 3500 X 2.3 = 8050 lineal feet of 1^4 inch pipe. 

Application 2. — The cooling of 180000 cubic feet of air per 
hour in Art. 211 required the extraction of 621600 B. t. u. per 
hour. Determine the plenum cooling surface required, if 
brine enters at degrees and leaves at 20 degrees. 

Average brine temperature = 10 degrees. Assuming 
that there is provision for leeping coils clear of ice, and 



HEFRiaE^RATION 213 

hence a transmission constant of 7 B. t. u. is allowable, 
formula 42 gives 

621600 

Rr =: = — 1691 square feet of surface. 

95 + 30) \ 
10 I 



'( 



The negative sign indicates a flow of heat in the direc- 
tion opposite to the flow in heating installations, for which 
the formula was primarily designed. 

213. General Application: — ^Considering the school build- 
ing and the table of calculated results on pages 202 to 205 
what amount of cooling coil surface would be required to 
keep the temperature of all rooms of this building at 73 
degrees on a day when the outside air temperature is 95 
degrees and the relative humidity 85 per cent.? 

Data Table XXV gives the total heat loss of the three 
floors of this building as 1483250 B. t. u. per hour on a zero 
day when the rooms are kept at 70 -degrees. Now this same 
building under the summer conditions would have delivered 
to it heat due to a temperature difference of 95 degrees — 73 
degrees = 22 degrees. Hence the total refrigeration loss dur- 

22 

ing the summer day would be approximately X 1483250 = 

70 

466000 B. t. u. per hour, which amount of heat would be used 
to warm the incoming air from some temperature up to 73 
degrees. Suppose the ventilation requirement of the build- 
ing is 2000000 cubic feet per hour. Since it requires ^V of 
a B. t u. to warm one cubic foot of air one degree, [2000000 
(73 — f)] ^ 55 = 466000, or * = 60.2, say 60 degrees. (See 
Arts. 36 and 38 and observe that the second term of the right 
hand member of formula 17 becomes a negative term). 

While ,the air is traversing the ducts between the coils 
and the rooms, allow a rise in temperature of 5 degrees. 
The coils would then be required to deliver 2000000 cubic 
feet of air per hour a^t 55 degrees when supplied wILth air at 
90 degrees and 85 per cent, humidity. To cool -this amount 
of air through the given range would require the absorption 
of (formula 9), [2000000 X (95 — 55)] -^ 55 = 1454500 B. t. u. 
At 95 degrees and 85 per cent, humidity, 1 cubic fooit of air 
contains (Table 10), .85 X 17.124 = 14.555 grains of moisture. 
At 55 degrees -and saturation point, 1 cubic foot of air con- 
tains (Table 10), 4.849 grains of moisture. Hence, neglecting 



314 HEATING AND VENTILATION 

change in air volume, there would be deposited on the coils 
approximately [2000000 (14.555 — 4.849)] 4- 7000 = 2775 
pounds of moisture per hour. 

Now, if an average brine temperature of 10 degrees is 
used and provision is made for keeping the coils clear of ice, 
the condensation will leave at some temperature above 10 
degrees, say 20 degrees, and there will be absorbed from 
each pound of this moisture approximately 

20 B. t. u. to cool from 95 to 55 degrees. 

1061 B. t. u. to change to liquid form at 55 degrees. 
35 B. t. u. to cool the water from 55 to 20 degrees. 



1116 B. t. u. total. 

Hence the coils would have to absorb from moisture alone, 
2775 X 1116 = 3096900 B. t. u., or from both moisture and air 
a total of 1454500 + 3096900 = 4551400 B. t. u. per hour. At 
an allowed rate of transmission of 7 B. t. u. there would be 
required to cool this building a total of approximately 9100 
square feet of coil surface, under the conditions of ventila^ 
tion as assumed. 

It should be noted that whereas only 3000 square feet 
of plenum surface were sufficient to heat the building ac- 
cording to Application 2, Art. 115, it requires fully three 
times this amount of surface in cooling coils to cool the 
building under the assumed conditions. Upon inspection it 
is seen that the greatest work of the cooling coils is the 
condensation and cooling of the moisture. 

The relative humidity within the cooled rooms would be 
approximately 55 per cent., for the content per cubic foot of 
incoming air is 4.849 grains, and the capacity of the air 
when heated to 73 degrees is 8.782 grains showing a relative 

4.849 

humidity, after heating, of = 55 per cent. This would 

8.782 

be raised somewhat by the persons present. 

214. Ice Making Capacity. Calculation: — Neglecting 
losses, the ice making capacity of a refrigerating plant for 
a certain refrigeration tonnage may be expressed 

144 T 

I - (107) 

it — 32) + 144 + .5 (32 — fi) 

in which 7 = tons of ice produced per 24 hours, 7*= refrig- 



REFRIGERATION 315 

eration tonnage or rating* of plant, t = initial temperature of 
water and t^ = final temperature of ice, usually 12 to 18 
degrees. 

Application. — What should be the ice making capacity of 
a plant having a tonnage rating of 100, if * == 70 degrees and 
^1 — 16 degrees? Take losses at 35 per cent. 

.65 X 144 X 100 

I — == 49.3 tons in 24 hours. 

(70 — 32) + 144 + .5 (32 — 16) 

215. Gallon Degree Calculation: — For use in plants pro- 
ducing ice by brine circulation a unit called the gallon degree 
is sometimes used. It represents a change of one degree 
temperature in 1 gallon of brine in one minute of time. 
It is not a fixed unit representing a constant num- 
ber of B. t. u., since the brine strength, and therefore its 
specific heat, may vary. The value in B. t. u. per minute, of 
a gallon degree for any plant may be obtained by multiply- 
ing the specific gravity of the brine by its specific heat and 
by 8.35, the weight of one gallon of water, or as a formula 
may be stated 

D — 8.35 gh (108) 

where D = B. t. u. per minute equal to one gallon degree, 
g = specific gravity of brine and li = specific heat of brine. 
The numher of gallon degrees per ton of refrigerating capacity may 
be found by dividing 200 by D, since one ton of refrigerating 
capacity is equal to 200 B. t. u. per minute, then 

200 24 

Dt — = for all practical purposes. (109) 

8.35 gJi gh - 

The refrigerating capacity of a given drine circulation may be 

obtained by dividing the product of the gallons circulated 

and the rise in brine temperature by the value Dt. Stated 

as a formula this is 

G (to — to) ghG (t2 — ts) 

T — — (110) 

Dt 24 

where T = tonnage capacity, G = gallons of brine circu- 
lated per minute and (^2 — ^3) = rise of brine temperature. 
216. Refrigerating Capacity of Brine Cooled System: — 

To calculate the capacity but two things are required, the 
amount of brine circulated, and the rise in temperature of 
the brine. From these the capacity may be obtained by 
the formula 



316 HEATING AND VENTILATION 

W h {to — ts) 
T = (111) 

12000 

where T = tonnage capacity, W = weight of brine circulated, 
in pounds, h = specific heat of brine and (^2 — ts) =■ rise in 
temperature of brine. 

217. Cost of Ice 3Iaking and Refrigeration: — The cost of 
ice manufacture is affected principally by the following 
items: price and kind of fuel, kind of water, cost of labor, 
regularity of operation, method of estimating costs, etc. 
It is found in practice to range anywhere from $0.50 to 
$2.50 per ton. The items making up the cost of ice manu- 
facture are: fuel for power, labor at the plant, water, am- 
monia and minor supplies, maintenance of the plant, inter- 
est and taxes, and administration. Mr. J. E. Siebel in his 
"Compend of Mechanical Refrigeration and Engineering"' 
gives an itemized account of the daily operating expense of 
a 100-ton plant with which he was connected, the plant 
operating 21 hours per day. 

Chief engineer $ 5.00 

Assistant engineers 6.00 

Firemen 4.00 

Helpers 5.00 

Ice pullers 9.00 

Expenses 12.00 

•Coal at $1.10 per ton 18.00 

Delivery (wholesale) 50c per ton 50.00 

Repairs, etc 3.00 

Insurance, taxes, etc .. 6.00 

Interest on capital 20.55 



Total for 100 tons of ice $138.55 

The length of time that the ice is permitted to freeze 
is a factor affecting the cost of production. The following 
figures are given for a 10-ton plant: 

Ten tons Ten tons 

in 12 hours in 24 hours 

Engineer $2.5a $ 5.00 

Fireman 1.50 3.00 

Tankmen, helpers . . 1.50 3.00 

Coal 3.00 3.00 

Repairs, supplies, etc. 1.50 1.50 



Total for 10 tons -$10.00 $15.50 



REFRIGERATION 317 

Mr. A. P. Criswell, in "Ice and Refrigeration," gives the 
following approximate costs for the production of can ice 
per ton with coal at $2.50 per ton and with a simple distill- 
ing system. The figures are for the plant operating at full 
capacity and do not include cost of administration. 

Capacitj' of plant Cost per ton 
10 tons $1.58 



20 
30 
40 
50 
70 
100 
120 



1.48 
1.42 
1.38 
1.36 
1.34 
1.34 
1.30 



Mr. Karl Wegemann states that a certain moderate sized 
plant of the absorption system produced ice for a number 
of years at an average cost of $0.85 per ton after allowing 
for melting and breakage. This included all charges ex- 
cept for interest, insurance and administration. 

The following figures taken from the books of another 
plant show clearly the effect of demand upon the cost of 
manufacture. 

Month Cost per ton 

January $3.50 

February 3.70 

March 2.80 

April 2.17 

May 1.75 

June 1.19 

July 1.02 

August 1.02 

September 1.03 

October 1.26 

November 2.10 

December 2.94 



318 HEATING AND VENTILATION 

REFERENCES. 
References on Refrigeration, 

Technical Books., 

A. J. Wallis-Taylor, Pocket-Booh of Refrigeration. John 
Wemyss Anderson, Refrigeration. James Alfred Ewing, Mechan- 
ical Refrigeration. J. E. Siebel, Compend of Mechanical Refriger- 
ation. International Library of Technology, pp. 643-966. I. C. S. 
Pamphlets, 1238 A, 1238 B, 1238 C, 1240, 1241, 1242, 1243, 
1246 A, 1246 B, 1247 and 1250. American School of Corre- 
spondence; Refrigeration, Dickerman & Boyer; Refrigeration, Mil- 
ton W. Arrowwood. 

Technical Periodicals. 

Ice and Refrigeration. The Ice Factory of the Future, Vic- 
tor H. Becker, Jan. 1910. Cell Box System for Making Raw 
Water Ice, A. C. Bishop, Dec. 1909. The P'looded System, H. 
Rassbach, Jan. 1910. Baker Chocolate Cooling- Plant, Aug. 
1910. The Working Fluid in Refrigeration, H. J. Maclntyre, 
Nov. 1910. Sulphur Dioxide as Refrigerating Agent, W. S. 
Douglas, Oct. 1911. Dry Blast Refrigeration, Nov. 1912. 
Power, Artificial Systems of Refrigeration, C. P. Wood, May 

3, 1910. Mechanical Refrigeration, F. E. Matthews, Aug. 9, 
1910. Elements of Compression System, F. E. Matthews, 
Sept. 6, 1910. Can and Plate Systems of Making Ice, F. E. 
Matthews, Mar. 14, 1911. Cold Storage of Furs and Fabrics, 
E. F. Tweedy, Feb. 20, 1912. Ammonia Absorption Refrig- 
eration System, Fred Ophuls, Apr. 23, 1912. Central Refrig- 
erating Plant at Atlanta, Georgia, May 7, 1912. Pre-Co-oling 
Plant of Southern Pacific Railway, LeRoy W. Allison, June 

4, 1912. Cooling Air of Buildings by Mechanical Refrigera- 
tion, E. F. Tweedy, Nov. 28, 1911. Electrical World, Ice Mak- 
ing from Exhaust Steam, Apr. 7, 1910. 



CHAPTER XVIII. 



PLANS AND SPECIFICATIONS FOR HEATING SYSTEMS, 



218. In Planning for and Executing Engineering Con- 
tracts, the responsibilities assumed by the various interested 
parties should be thoroughly studied. The following outline 
shows the relationship between these parties and the order 
of the responsibility. 

^ /Engineer. 

Owner | ^ . 

I Superintendent and Inspector. 
or / 

T-. , \ General contractor, Subcontractors, Foremen and 

Purchaser I 

I Workmen. 

The engineer, the superintendent and the general con- 
tractor occupy positions of like responsibility with relation 
to the purchaser. The first two work for the interest of the 
purchaser to obtain the best possible results for the least 
money, and the last endeavors to fulfill the contract to the 
satisfaction of the superintendent, at the least possible ex- 
pense to himself. These points of view are quite different 
and sometimes are antagonistic, but both are right and just. 
Of the three parties, the engineer has the greatest respon- 
sibility. It is his duty to draw up the plans and to write 
the specifications in such a way that every point is made 
clear and that no .question of dispute may arise between the 
superintendent and the contractor. His plans should detail 
every part of the design with full notes. His specifications 
should explain all points that are difficult to delineate on the 
plans. They should give the purchaser's views covering all 
preferences, and should definitely state where and what ma- 
terials may be substituted. Where any point is not definitely 
settled and left to the judgment of. the contractor, he may 
be expected to interpret this point in his favor and use the 
cheapest material that in his judgment will give good re- 
sults. This opinion may differ from that held by the pur- 
chaser. All parts should be made so plain that no two opin- 
ions could be had on any important point. The engineer 
should also be careful that the plans and specifications agree 
in every part. The inspector is the superintendent's repre- 
sentative on the grounds and is supposed to inspect and 
pass upon all materials delivered on the grounds, and the 



520 HEATING AND VENTILATION 

quality of workmanship in installing-. For such information 
see Byrne's ''Inspector's Pocket-Book." The general con- 
tractor usually sublets parts of the contract to subcon- 
tractors who work throug-h the foreman and workmen to 
finish the work upon the same basis as the g-eneral con- 
tractor. 

The following- brief set of specifications are not con- 
sidered complete but are merely inserted to sugg-est how 
such work is done. 

Typical Specifications. 

Title Page: — 

SPECIFICATIONS 

for the 

MATEKIALS AND WORKMANSHIP 

Required to Install 



(Type of system) 

HEATING AND VENTILATING SYSTEM 

in the 



(Building) 



(Location) 
by 



(Name of designer) 
Index Page: — 

(To be compiled after the specifications are TSTritten.) 

General Remarks to Contractor. — In the following specifi- 
cations, all -references to the Owner or Purchaser will mean 

or any p&rson or persons delegated by 

to serve as the representative. The Super- 
intendent of Buildings will be the purchaser's representative at 
all times, unless otherwise definitely stated. The contractor 
will, therefore, refer all doubtful questions or misunder- 



TYPICAL SPECIFICATIONS 321 

standings, if any, to the superintendent, whose decision will 
be final. In case of any doubt concerning- the meaning' of 
any part of the plans or specifications, the contractor shall 
obtain definite interpretation from the superintendent be- 
fore proceeding with the work. 

These specifications with the accompanying plans and 
details (sheets .... to .... inclusive) cover the purchase of 
all the materials as specified later (the same materials to 
be new in every case), and the installation of the same in a 
first class manner within the above named building", located 
at (street) .... (city) (state). 

It will be understood that the successful bidder, herein- 
after called the contractor, shall work in conformity with 
these plans and specifications and shall, to the best of his 
ability, carry out their true intent and meaning. He shall 
purchase and erect all materials and apparatus required to 
m'ake the above system complete in all its parts, supplying 
only such quality of materials and workmanship as will har- 
monize TV^ith a first class system and develop satisfactory 
results when working under the heaviest service to which 
such plants are subjected. 

The contractor shall lay out his own work and be re- 
sponsible for its fitting to place. He shall keep a competent 
foreman on the grounds and shall properly protect his work 
at all times, making good any damage that may comie to it, 
or to the building, or to the work of other contractors from 
any source whatsoever, which may be chargeable to himself 
or to his employees in the course of their operations. 

Any defects in materials or workmanship, other than 
as stated under — (state exceptions if any) — ^^that may develop 
within one year, shall be made good by the contractor upon 
written notification from the purchaser without additional 
cost to 'the purchaser. 

The contractor shall, wherever it is found necessary, 
make all excavations and back-fill to the satisfaction of the 
superintendent. 

The contractor shall be responsible for all cuttings of 
wood work, brick work or cement work, found necessary 
in fitting his materials to place, either within or without the 
building; the cutting to be done to the satisfaction of the 
superintendent. The contractor shall be required to connect 
and supply water and gas for building purposes, and shall 



322 HEATING AND VENTILATION 

assume all responsibility for the same. 

The contractor shall be required to protect the purchaser 
from damage suits, originating from personal injuries re- 
ceived during the progress of the work; also, from actions 
at law because of the use of patente'd articles furnished by 
the contractor; also, from any lien or liens arising because 
of any materials or labor furnished. 

The purchaser reserves the right to reject any or all 
bids. 

No changes in these plans and specifications will be 
allowed except upon written agreement signed by both the 
contractor and the purchaser's representative. 

System. — Specify the system of heating in a general way; 
high pressure, low pressure or vacuum; direct, direct-indi- 
rect or indirect radiation; basement or attic mains; one 
or two-pipe connections to radiators. If ventilation is 
provided, state the movement of the air and the general 
arrangement of fans, coils or other heating surfaces. Single 
or double duct air lines, etc. 

Boilers. — Specify type, number, size and capacity, steam, 
pressure, approximate horse-power, heating surface, grate 
surface and kind of coal to be used. Locate on plan and ele- 
vation. Explain method of setting, portable or brick. 
Specify also, flue connection, heating and water pipe con- 
nections, kind of grate, thermometers, gages, automatic 
damper connection, firing tools and conditions of final tests. 

Conduits and Conduit Mains. — (In this it is assumed that the 
boilers are not within the building). In addition to the lay- 
out, give sections of the conduit on plans showing method 
of construction, supporting and insulating pipes, and drain- 
age of pipes and conduits. Specify quality and size of mate- 
rials, pitch and drainage of pipes and all other points not 
specially provided for in the plans. 

Anchors. — Locate and draw on plans and specify for the 
installation regarding quality of materials. 

Expansion Joints or Take-ups. — Locate and draw on plans. 
Select type of joint and specify for amount of safe take-up 
and for quality of material. 

Mains and Returns. — Trace the steam from the point where 
it enters the main, through all the special fittings of the 

system. Show where the condensation is dripped 

to the returns through traps or separating devices. Specify 



TYPICAL SPECIFICATIONS 323 

amount and direction of pitch, kind of fitting-s (flanged or 
screwed, cast iron or malleable iron), kind of corners (long 
or short), method of taking up expansion and contraction. 
Trace returns and specify dry or wet. 

Branches to Risers. — Take branches from top of mains by 
tees, short nipples and ells, and enter the bottom of the 
risers by sufficient inclination to give good drainage. 

Risers. — Locate risers according to plan. They shall be 
straight and plumb and shall conform to the sizes given on 
the plans. No riser shall overlap the casing around win- 
dows. State how branches are to be taken off leading to 
radiators, relative to the ceiling or floor. 

Radiator Connections. — ^Specify, one-pipe or two-pipe, num- 
ber and kind of valves, sizes of connections and hand or 
automatic control. All connections shall allow for good 
drainage and expansion. Distinguish between wall radiator 
and floor radiator connections. If automatic control is used, 
hand valves at the radiators are usually omitted. 

Radiators. — Specify floor or wall radiators, with type, 
height, number of columns and number of sections. If other 
radiators are substituted for the ones that are referred to 
as acceptable, they must be of equal amount of surface and 
acceptable to the superintendent. Specify brackets for wall 
radiators, also, air valves for all radiators, stating type 
and location on the radiator. Require all radiators to be 
cleaned with water or steam at the factory and plugged at 
inlet and outlet for shipment. 

Piping. — Define quality, weight and material in all mains, 
branches and risers. All sizes above one and one-half inch 
are usually lap welded. Piping should be stood on end and 
pounded to remove all scale before going into the system. 
All pipes 1 inch and smaller should be reamed out full size 
after cutting. 

Fittings. — Specify quality of fittings, whether light, stand- 
ard or heavy, malleable or cast iron. Fittings with imper- 
fect threads should be rejected. 

Valves. — Specify type (globe, gate or check), whether 
flanged or screwed, rough or smooth body, cast iron or 
brass, and give pressure to be carried. All valves should 
be located on the plans. 

Expansion Tank. — Specify capacity of tank in gallons, kind 



324 HEATING AND VENTILATION 

of tank (square or round, wood or steel), method of connect- 
ing- up with fittings and valves, and locate definitely on plan 
and elevation. Connect also to fresh water supply and to 
overflow. 

Hangers and Ceiling Plates. — Wall radiators and horizontal 
runs of pipe shall be supported on suitable expansion hang- 
ers or wall supports that w^ill permit of absolute freedom of 
expansion. Supports shall be placed .... feet centers. Pipe 
holes in concrete floors shall be thimbled. Holes through 
wooden walls and floors shall have suitable air space around 
the pipe, and all openings shall be covered with ornamental 
floor, ceiling or wall plates. 

Traps. — Specify type, size, capacity and, location. State 
whether flanged or screwed fittings are used and whether 
by-pass connection will be put in. Refer to plans. 

Pressure Regulating Yalve. — iSpecify type, size and location, 
also maximum and minimum steam pressure, with guaran- 
tee to operate under slight change of pressure. State if 
by-pass should be used and explain with plans. 

Separators. — Specify type (horizontal or vertical), also 
size and location. 

Automatic Control. — The contractor will be held responsible 
for ithe installation of all thermostats, regulator valves, air 
compressor, piping and fittings required to equip all rooms 
and halls with an automatic .... temperature control sys- 
tem. Specify approximate location and number of thermo- 
stats with the desired finish. Specify in a general way, reg"- 
ulator valves on radiajtors, quality of pipe, maximum test 
pressure for pipe, power for air supply (hydraulic, pneu- 
matic, etc.), and supply tank. All materials in the tem- 
perature control system shall be guaranteed first class by 
the manufacturer through the contractor, and the system 
shall be guaranteed to give perfect control for a period of 
(two) years. 

Fans. — Specify for direct connected or belt driven, right 
or left hand, capacity, size, housing, direction of discharge, 
horse-power, R. P. M. and pressure. State in a general way 
the requirements of the fan wheel, steel plate housing, shaft, 
bearings and the method of lubrication. 

Engine. — Specify type, horse-power, steam pressure, ap- 
proximate cut-off, speed and kind of control. 



TYPICAL SPECIFICATIONS 325 

Electric Motors. — Specify type, horse-power, voltage, cycles, 
phases and R. P. M, 

Indirect Heating Surface. — ^^Specify the kind of surface to 
be put in and then state the total number of square feet 
of surface, with the width, height and depth of the heater. 
Staite definitely how the heaters will be assembled, giving 
free height of heater above the floor. Describe damper con- 
trol, steam piping to and from heater, housing around heater, 
connection from cold air inlet to heater and connection from 
heater to fan. See plans. The contractor will usually follow 
installaition instructions given by the manufacturers for the 
erection of the heater and engine, consequently the speci- 
fications should bear heavily only upon those points which 
may be varied to suit any condition. All valves, piping and 
fittings in this work should be controlled by the general 
specifications referring to these parts. 

Foundations. — Specify materials and sizes. 

Air Ducts, Stacks and Galvanized Iron Work. — The drawings 
should give the layout of all the air lines, giving connections 
between the air lines and the fan, and the air lines and the 
registers. Where these air lines are below the floor, the 
conduit construction should be carefully noted. All gal- 
vanized iron work should be shown on the plans and the 
quality and weight should be specified. Air lines should 
have long radius turns at the corners. 

Registers. — Specify height above floor, nominal size of 
register, method of fitting in wall, the finish of the regis- 
ter and whether fitted with shutters or not. 

Protection and Covering. — Specify kind and quality of pipe 
covering and the finish of the surface of the covering. State 
the amount of space between heating pipes and unprotected 
woodwork. Distinguish between pipes that are to be covered 
and those that are to be painted. All radiators and piping 
not covered should be painted with two coats of .... bronze 
or other finish acceptable to the superintendent. 

Completion. — Require all rubbish removed from the build- 
ing and immediate grounds and deposited at a definite place. 



APPENDIX 
I 



GENERAL TABLES. 
HEATING AND VENTILATION. 



Tables in body of text are numbered in Roman 
numerals, those in the Appendixes are numbered in 
Arabic numerals. 

All tables that are not considered general are credited 
and added by permission of the authors. 



327 



TABLE 1. 
Squares, Cubes, Square Roots, Cube Roots, Circles. 













Cirri A 


No. 


Square 


Cube 


Sq. 
root 


Cube 
root 






Diam. 


Circumf 


Area 


.1 


.010 


.001 


.316 


.464 


.314 


.00785 


.2 


.040 


.008 


.447 


.585 


.628 


.03146 


.3 


.090 


.027 


.548 


.669 


.942 


.07069 


.4 


.160 


.064 


.633 


.737 


1.257 


.12566 


.5 


.250 


.125 


.707 


.794 


1.570 


.19635 


.6 


.360 


.216 


.775 


.843 


1.885 


.28274 


.7 


.490 


.343 


.837 


.888 


2.200 


.38485 


.8 


.640 


.512 


.894 


.928 


2.513 


.50266 


.9 


.810 


.729 


.949 


.965 


2.830 


.63620 


1.0 


1.000 


1.000 


1.000 


1.000 


3.1416 


.7854 


1.1 


1.210 


1.331 


1.0488 


1.0323 


3.456 


.9503 


1.2 


1.440 


1.730 


1.0955 


1.0627 


3.770 


1.1310 


1.3 


1.690 


2.197 


1.1402 


1.0914 


4.084 


1.3273 


1.4 


1.960 


2.744 


1.1832 


1.1187 


4.398 


1.5394 


1.0 


2.250 


3.375 


1.2247 


1.1447 


4.712 


1.7672 


1.6 


2.560 


4.096 


1.2649 


1.1696 


5.027 


2.0106 


1.7 


2.890 


4.913 


1.3038 


1.1935 


5.341 


2.2698 


1.8 


3.240 


5.832 


1.3416 


1.2164 


5.655 


2.5447 


1.9 


3.610 


6.859 


1.3784 


1.2386 


5.969 


2.8353 


2.0 


4.000 


8.000 


1.4142 


1.2599 


6.283 


3.1416 


2.1 


4.410 


9.261 


1.4491 


1.28U6 


6.597 


3.4636 


2.2 


4.840 


10.648 


1.4832 


1.3006 


6.912 


3.8013 


2.3 


5.290 


12.167 


1.5166 


1.3200 


7.226 


4.1548 


2.4 


5.760 


18.824 


1.5492 


1.3389 


7.540 


4.5239 


2.5 


6.250 


15.625 


1.5811 


1.3572 


7.854 


4.9087 


2.6 


6.760 


17.576 


1.6125 


1.3751 


8.168 


5.3093 


2.7 


7.290 


19.683 


1.6432 


1.3925 


8.482 


5.7256 


2.8 


7.840 


21.952 


1.6733 


1.4095 


8.797 


6.1575 


2.9 


8.410 


24.389 


1.7029 


1.4260 


9.111 


6.6052 


3.0 


9.000 


27.000 


1.7321 


1.4422 


9.425 


7.0688 


3.1 


9.610 


29.791 


1.7607 


1.4581 


9.739 


7.5477 


3.2 


10.240 


32.768 


1.7889 


1.4736 


10.053 


8.0125 


3.3 


10.890 


35.9.37 


1.8166 


1.4888 


10.367 


8.5530 


3.4 


11.560 


39.304 


1.8439 


1.5037 


10.681 


9.0792 


3.5 


12.250 


42.875 


1.8708 


1.5183 


10.996 


9.6211 


3.6 


12.960 


46.656 


1.8974 


1.5326 


11.310 


10.179 


3.7 


13.690 


50.653 


1.9235 


1.5467 


11.624 


10.752 


3.8 


14.440 


54.872 


1.9494 


1.5605 


11.938 


11.341 


3.9 


15.210 


59.319 


1.9748 


1.5741 


12.252 


11.946 


4,0 


16.000 


64.000 


2.0000 


1.5870 


12.566 


12.566 


4.1 


16.810 


68.921 


2.0249 


1.6005 


12.881 


13.203 


4.2 


17.640 


74.088 


2.0494 


1.6134 


13.195 


13.854 


4.3 


18.490 


79.507 


2.0736 


1.6261 


13.509 


14.522 


4.4 


19.360 


85.184 


2.0976 


1.6386 


13.823 


15.205 



328 



No. 


Square 


Cube 


Sq. 
root 


Cube 
root 


Circle 


Diam. 


Olrcumf 


Area 


4.5 


20.250 


91.125 


2.1213 


1.6510 


14.137 


15.904 


4.6 


21.160 


97.336 


2.1448 


1.6631 


14.451 


16.619 


4.7 


22.090 


103.823 


2. 1680 


1.6751 


14.765 


17.349 


4.8 


23.040 


110.592 


2.1909 


1.6869 


15.080 


18.096 


4.9 


24.010 


117.649 


2.2136 


1.6985 


15.394 


18.859 


5.0 


25.000 


125.000 


2.2361 


1.7100 


15.708 


19.635 


5.1 


26.010 


132.651 


2.2583 


1.7213 


16.022 


20.428 


5.2 


27.040 


140.608 


2.2804 


1.7325 


16.336 


21.237 


5.3 


28.090 


148.877 


2.3022 


1.7435 


16.650 


22.062 


5.4 


29.160 


157.464 


2.3238 


1.7544 


16.965 


22.902 


5.5 


30.250 


166.375 


2.3452 


1.7652 


17.279 


23.758 


5.6 


31.360 


175.616 


2.3664 


1.7760 


17.593 


24.630 


5.7 


32.490 


185.193 


2.3S75 


1.7863 


17.907 


25.518 


5.8 


33.640 


195.112 


2.4083 


1.7967 


18.221 


26.421 


5.9 


34.810 


205.379 


2.4290 


1.8070 


18.536 


27.340 


6.0 


36.000 


216.000 


2.4495 


1.8171 


18.850 


28.274 


6.1 


37.210 


226.981 


2.4698 


1.8272 


19.164 


29.225 


6.2 


38.440 


238.328 


2.490O 


1.8371 


19.478 


30.191 


6.3 


39.690 


250.047 


2.5100 


1.8469 


19.792 


31.173 


6.4 


40.960 


262.144 


2.5298 


1.8566 


20.106 


32.170 


6.5 


42.250 


274.625 


2.5495 


1.8663 


20.420 


33.183 


6.6 


43.560 


287.496 


2.5691 


1.8758 


20.735 


34.212 


6.7 


44.890 


300.763 


2.5884 


1.8852 


21.049 


35.257 


6.8 


46.240 


314.432 


2.6077 


1.8945 


21.363 


36.317 


6.9 


47.610 


328.509 


2.6268 


1.9038 


21.677 


37.393 


7.0 


49.000 


343.000 


2.6458 


1.9129 


21.991 


38.485 


7.1 


50.410 


357.911 


2.6646 


1.9220 


22.305 


39.592 


7.2 


51.840 


373.248 


2.6833 


1.9310 


22.619 


40.715 


7.3 


53.290 


389.017 


2.7019 


1.9399 


22.934 


41.854 


7.4 


54.760 


405.224 


2.7203 


1.9487 


23.248 


43.008 


7.5 


56.250 


421.875 


2.7386 


1.9574 


23.562 


44.179 


7.6 


57.760 


438.976 


2.7568 


1.9661 


23.876 


45.365 


7.7 


59.290 


456.533 


2.7749 


1.9747 


24.190 


i6.566 


7.8 


60.840 


474.552 


2.7929 


1.9832 


24.504 


47.784 


7.9 


62.410 


493.039 


2.8107 


1.9916 


24.819 


49.017 


8.0 


64.000 


512.000 


2.8284 


2.0000 


25.133 


50.266 


8.1 


65.610 


531.441 


2.8461 


2.0083 


25.447 


51.530 


8.2 


67.240 


551.468 


2.8636 


2.0165 


25.761 


52.810 


8.3 


68.890 


571.787 


2.8810 


2.0247 


26.075 


54.106 


8.4 


70.560 


592.704 


2.8983 


2.0328 


26.389 


55.418 


8.5 


72.250 


614.125 


2.9155 


2.0408 


26.704 


56.745 


8.6 


73.960 


636.056 


2.9326 


2.0488 


27.018 


58.088 


8.7 


75.690 


658.503 


2.9496 


2.0567 


27.332 


59.447 


8.8 


77.440 


681.473 


2.9665 


2.0646 


27.646 


60.821 


8.9 


79.210 


704.969 


2.9833 


2.0724 


27.960 


62.211 



329 













Oirole 


No. 


Square 


OubQ 


root 


Cube 
root 






Diam. 


Oircumf 


Area 


9.0 


81.000 


729.000 


3.0000 


2.0801 


28.274 


63.617 


9.1 


82.810 


753.571 


3.0166 


2.0878 


28.588 


65.039 


9.2 


84.640 


778.688 


3.0332 


2.0954 


28.903 


66.476 


9.3 


86.490 


804.357 


3.0496 


2.1029 


29.217 


67.929 


9.4 


88.360 


830.584 


3.0659 


2.1105 


29.531 


69.398 


9.5 


90.250 


857.375 


3.0822 


2.1179 


29.845 


70.882 


9.6 


92.160 


884.736 


3.0984 


2.1253 


30.159 


72.382 


9.7 


94.090 


912.673 


3.1145 


2.1327 


30.473 


73.898 


9.8 


96.040 


941.192 


3.1305 


2.140O 


30.788 


75.430 


9.9 


98.010 


970.299 


3.1464 


2.1472 


31.102 


76.977 


10 


100.000 


1000.000 


3.1623 


2.1544 


31.416 


78.540 


11 


121.000 


1331.000 


3.3166 


2.2239 


34.558 


95.033 


12 


144.000 


1728.000 


3.4641 


2.2894 


37.690 


113.097 


13 


169.000 


2197.000 


3.6056 


2.3513 


40.841 


132.732 


14 


196.000 


2744.000 


3.7417 


2.4101 


43.982 


153.938 


15 


225.000 


3375.000 


3.8730 


2.4662 


47.124 


176.715 


16 


256.000 


4096.000 


4.00O0 


2.5198 


50.265 


201.062 


17 


289.000 


4913.000 


4.1231 


2.5713 


53.407 


226.980 


18 


324.000 


5832.000 


4.2426 


2.6207 


56.519 


254.469 


19 


361.000 


6859.000 


4.3589 


2.6684 


59.690 


283.529 


20 


400.000 


8000.000 


4.4721 


2.7144 


62.832 


314.159 


21 


441.000 


9261.000 


4.5826 


2.7589 


65.793 


346.361 


22 


484.000 


10648.000 


4.6904 


2.8021 


69.115 


380.133 


23 


529.000 


12167.000 


4.7958 


2.&139 


72.257 


415.476 


24 


576.000 


13824.000 


4.8990 


2.8845 


75.398 


452.389 


25 


625.000 


15625.000 


5.0000 


2.9241 


78.540 


490.874 


26 


676.000 


17576.000 


5.0990 


2.9625 


81.681 


530.929 


27 


729.000 


19683.000 


5.1962 


3.0000 


84.823 


572.555 


28 


784.000 


21952.000 


5.2915 


3.0366 


87.965 


615.752 


29 


841.000 


24389.000 


5.3852 


3.0723 


91.106 


660.520 


SO 


900.000 


27000.000 


5.477'^ 


3.1072 


94.248 


706.858 


31 


961.000 


29791.000 


5.5678 


3.1414 


97.389 


754.768 


32 


1024.000 


32768.000 


5.6569 


3.1748 


100.531 


801.248 


33 


1089.000 


35937.000 


5.7446 


3.2075 


103.673 


855.299 


34 


1156.000 


39304.000 


5.8310 


3.2396 


106.841 


907.920 


35 


1225.000 


42875.000 


5.9161 


3.2710 


109.956 


962.113 


36 


1296.000 


46656.000 


6.0000 


3.3019 


113.097 


1017.88 


37 


1369.000 


50653.000 


6.0827 


3.3322 


116.239 


1075.21 


38 


1444.000 


54872.000 


6.1644 


3.3620 


119.381 


1134.11 


39 


1521.000 


59319.000 


6.2450 


3.3912 


122.522 


119i.59 


40 


1600.000 


64000.000 


6.3246 


3.4200 


125.66 


1256.64 


41 


1681.000 


68921.000 


6.4031 


3.4482 


128.81 


1320.25 


42 


1764.000 


74088.000 


6.4807 


3.4760 


131.95 


1385.44 


43 


1849.000 


79507.000 


6.5574 


3.5034 


135.09 


1452.20 


44 


1936.000 


85184.000 


6.6333 


3.5303 


138.23 


1520.53 



330- 













CirplA 


No. 


Square 


Cube 


Sq. 
root 


Cube 
root 






Diam. 


Circumf 


Area 


45 


2025.000 


91125.000 


6.7082 


3.5569 


141.37 


1590.43 


46 


2116.000 


97336.000 


6.7823 


3.5830 


144.51 


1651.90 


47 


2209.000 


103823.000 


6.8557 


3.6088 


147.65 


1734.94 


48 


2304.000 


110592.000 


6.92S2 


3.6342 


150.80 


1809.56 


49 


2401.000 


117649.000 


7.0000 


3.6593 


153.94 


. 1885.74 


50 


2500.000 


125000.000 


7.0711 


3.6840 


157.08 


1963.50 


51 


2601.000 


132651.000 


7.1414 


3.7084 


160.22 


2042.82 


52 


2704.000 


140608.000 


7.2111 


3.7325 


163.36 


2123.72 


53 


2809.000 


148877. OOO 


7.2801 


3.7563 


166.50 


2206.18 


54 


2916.000 


157464.000 


7.3485 


3.7798 


169.65 


2290.22 


55 


3025.000 


166375.000 


7.4162 


3.8030 


172.79 


2375.83 


56 


3136.000 


175616.000 


7.4833 


3.8259 


175.93 


2463.01 


57 


3249 000 


185193.000 


7.5498 


3.8485 


179.07 


2551.76 


58 


3364.000 


195112.000 


7.6158 


3.8709 


182.21 


2642.08 


59 


3481.000 


205379.000 


7.6811 


3.8930 


185.35 


2733.97 


60 


3600.000 


216000.000 


7.7460 


3.9149 


188.50 


2827.43 


61 


3721.000 


226981.000 


7.8102 


3.9365 


191.64 


2922.47 


62 


3844.000 


238328.030 


7.8740 


3.9579 


194.78 


3019.07 


63 


3969.000 


250047.000 


7.9373 


3.9791 


197.92 


3117.25 


64 


4096.000 


262144.000 


8.0000 


4.0000 


201.06 


3216.99 


65 


4225.000 


274625.000 


8.0623 


4.0207 


204.20 


3318.31 


66 


4356.000 


287496.000 


8.1240 


4.0412 


207.34 


3421.19 


67 


4489.000 


300763.000 


8.1854 


4.0615 


210.49 


3525.65 


68 


4624.000 


314432.000 


8.2462 


4.0817 


213.63 


3631.63 


69 


4761.000 


328509.000 


8.3066 


4.1016 


216.77 


3739.28 


70 


4900.000 


343000.000 


8.S666 


4.1213 


219.91 


3848.45 


71 


5041.000 


357911.000 


8.4261 


4.1408 


223.05 


3959.19 


72 


5184.000 


373248.000 


8.4853 


4.1602 


226.19 


4071.50 


73 


5329.000 


389017.000 


8.5440 


4.1793 


229.34 


4185.39 


74 


5476.000 


405224.000 


8.6023 


4.1983 


232.48 


4300.84 


75 


5625.000 


421875.000 


8.6603 


4.2172 


235.62 


4417.86 


76 


5776. OOO 


438976.000 


8.7178 


4.2358 


238.76 


4536.46 


77 


5929.000 


456533.000 


8.7750 


4.2543 


241.90 


4656.63 


78 


6084.000 


474552.000 


8.8318 


4.2727 


245.04 


4778.36 


79 


6241.000 


493039.000 


8.8882 


4.2908 


248.19 


4901.67 


80 


6400.000 


512000.000 


8.9443 


4.3089 


251.33 


5026.55 


81 


6561.000 


531441.000 


9.000O 


4.3267 


254.47 


5153.00 


82 


6724.000 


551368.000 


9.0554 


4.3445 


257.61 


5281.02 


83 


6889.000 


571787.000 


9.1104 


4.3621 


260.75 


5410.61 


84 


7056.000 


592704.000 


9.1652 


4.3795 


263.89 


5541.77 


85 


7225.000 


614125.000 


9.2195 


4.39<:: 


267.04 


5674.50 


86 


7396.000 


636056.000 


9.2736 


4.4140 


270.18 


5808.80 


87 


7569.000 


658503.000 


9.3274 


4.4310 


273.32 


5944.68 


88 


7744.000 


681472.000 


9.3808 


4.4480 


276.46 


6082.12 


89 


7921.000 


704969.000 


9.4340 


4.4647 


279.60 


6221.14 



331 



No. 
Biam. 


Square 


Cube 


Sq. 
root 


Cube 
root 



Oircumf 


ircle 
Area 


90 


8100.000 


729000.000 


9.4868 


4.4814 


282.74 


6361.73 


91 


828 L. 000 


753571.000 


9.5394 


4.4979 


285.88 


6503.88 


92 


8464.000 


778688.000 


9.5917 


4.5144 


289.03 


6647.61 


93 


8649.000 


804357.000 


9.6437 


4.5307 


292.17 


6792.91 


94 


8836.000 


830584.000 


9.6954 


4.5468 


295.81 


6939.78 


95 


9025.000 


857375.000 


9.7468 


4.5629 


298.45 


7088.22 


96 


9216.000 


884736.000 


9.7980 


4.5789 


301.59 


7238.23 


97 


9409.000 


912673.000 


9.8489 


4.5947 


304.73 


7389.81 


98 


9604.000 


941192.000 


9.8995 


4.6104 


307.88 


7542.96 


99 


9801.000 


970299.000 


9.9499 


4.6261 


311.02 


7697.69 


100 


10000. OOO 


1000000. 000 


10.0000 


4.6416 


314.16 


7853.98 


105 


11025.000 


1157625.000 


10.2470 


4.7177 


329.87 


8659.01 


110 


12100.000 


1331000.000 


10.4881 


4.7914 


345.58 


9503.32 


115 


13225.000 


1520875.000 


10.7238 


4.8629 


361.28 


10386.89 


120 


14400.000 


1728000.000 


10.9545 


4.9324 


376.99 


11309.73 


125 


15625.000 


1953125.000 


11.1803 


5.0000 


392.70 


12271.85 


130 


16900.000 


2197000.000 


11.4018 


5.0658 


408.41 


13273.23 


135 


18225.000 


2460375.000 


11.6190 


5.1299 


424.12 


14313.88 


140 


19600.000 


2744000.000 


11.8322 


5.1925 


439.82 


15393.80 


145 


21025.000 


3048625.000 


12.0416 


5.2536 


455.53 


16513.00 


150 


22500.000 


3375000.000 


12.2474 


5.3133 


471.24 


17671.46 


155 


24025.000 


3723875.000 


12.4499 


5.3717 


486.95 


18869.19 


160 


25600.000 


4096000.000 


12.6491 


5.4288 


502.65 


20106.19 


165 


27225.000 


4492125.000 


12.8452 


5.4848 


518.36 


21382.46 


170 


28900.000 


4913000.000 


13.0384 


5.5397 


534.07 


22698.01 


175 


30625.000 


5359375.000 


13.2288 


5.5934 


549.78 


24052.82 


180 


32400.000 


5832000.000 


13.4164 


5.6462 


565.49 


25446.90 


185 


34225.000 


6331625.000 


13.6015 


5.6980 


581.19 


26880.25 


190 


36100.000 


6859000.000 


13.7840 


5.7489 


596.90 


28352.87 


195 


38025.000 


7414875.000 


13.9642 


5.7989 


612.61 


29864.77 


200 


40000.000 


8000000.000 


14.1421 


5.8480 


628.32 


31415.93 


205 


42025.000 


8615125.000 


14 3178 


5.8964 


644.03 


33006.36 


210 


44100.000 


9261000.000 


14.4914 


5.9439 


659.73 


34636.06 


215 


46225.000 


9938375.000 


14.6629 


5.9907 


675.44 


36305.01 


220 


48400.000 


10648000.000 


14.8324 


6.0368 


691.15 


38013.27 


225 


50625.000 


11390625.000 


15.0000 


6.0822 


706.86 


39760.78 


230 


, 52900.000 


12167000.000 


15.1658 


6.1269 


722.57 


41547.56 


235 


55225.000 


12977875.000 


15.3297 


6.1710 


738.27 


43373.61 


240 


57600.000 


13824000.000 


15.4919 


6.2145 


753.98 


45238.93 


245 


60025.000 


14706125.000 


15.6525 


6.2573 


769.69 


47143.52 


250 


62500.000 


15625000.000 


15.8114 


6.2996 


785.40 


49087.39 


255 


65025.000 


16.581375.000 


15.9687 


6.3413 


801.11 


51070.52 


260 


67600.000 


17576000.000 


16.1245 


6.3825 


816.81 


53092.92 


265 


70225.000 


18609625.000 


16.2788 


6.4232 


832.52 


55154.59 


270 


72900.000 


19683000.000 


16.4317 


6.4633 


848.23 


57255.53 



?32 



No. 


Square 


Cube 


Sq. 
root 


Cube 
root 


Circle 


Diam. 


Circumf 


Area 


275 


75625.000 


20796875.000 


16.5831 


6.5030 


863.94 


59895.74 


280 


78400.000 


21952000.000 


16.7332 


6.5421 


879.65 


61575.22 


285 


81225.000 


23149125.000 


16.8819 


G.5S0S 


895.35 


63793.97 


290 


84100.000 


24389000.000 


17.0294 


6.6191 


911.06 


66051.99 


295 


87025.000 


25672375.000 


17.1756 


6.6569 


926.77 


68349.28 


SCO 


90000.000 


27000000.000 


17.3205 


6.6943 


942.48 


70685.83 


805 


93025.000 


28372625.000 


17.4642 


6.7313 


958.19 


73061.63 


SIO 


96100.000 


29791000.000 


17.6068 


6.7679 


973.89 


75476.76 


815 


99225.000 


31255875.000 


17.7482 


6.8041 


989.60 


77931.13 


820 


102400.000 


82768000.000 


17.8885 


6.8399 


1005.31 


80424.77 


825 


105625.000 


34328125.000 


18.0278 


6.8753 


1021.02 


82957.68 


830 


108900.000 


85937000.000 


18.1659 


6.9104 


1036.73 


85529.86 


835 


112225.000 


37595375.000 


18.3030 


6.9451 


1052.43 


88141.31 


840 


115600.000 


89304000.000 


18.4391 


6.9795 


1068.14 


90792.03 


845 


119025.000 


41063625.000 


18.5742 


7.0136 


1083.85 


93482.02 


850 


122500.000 


42875000.000 


18.7083 


7.0473 


1099.56 


96211.23 


855 


126025.000 


44738875.000 


18.8414 


7.0807 


1115.27 


98979.80 


860 


129600:000 


46656000.000 


18.9737 


7.1138 


1130.97 


101787.60 


865 


133225.000 


48627125.000 


19.1050 


7.1466 


1146.68 


104634.67 


870 


136900.0^)0 


50653000.000 


19.2354 


7.1791 


1162.39 


107521.01 


875 


140625.000 


52734375.000 


19.3649 


7.2112 


1178.10 


110446.62 


880 


144400.000 


54872000.000 


19.4936 


7.2482 


1193.81 


113411.49 


885 


148225.000 


57066625.000 


19.6214 


7.2748 


1209.51 


116415.64 


890 


152100.000 


59319000.000 


19.7484 


7.3061 


1225.22 


119459.06 


895 


156025. 000 


61629875.000 


19.8746 


7.3372 


1240.93 


122541.75 


400 


160000.000 


64000000.000 


20.0000 


7.3681 


1256.64 


125663.71 


405 


164025.000 


66430125.000 


20.1246 


7.3986 


1272.35 


128824.93 


410 


168100.000 


68921000.000 


20.2485 


7.4290 


1288.05 


132025.43 


415 


172225.000 


71473375.000 


20.3715 


7.4590 


1303.76 


135265.20 


420 


176400.000 


74088000.000 


20.4939 


7.4889 


1319.47 


138544.24 


425 


180625.000 


76765625.000 


20.6155 


7.5185 


1335.18 


141862.54 


430 


184900.000 


79507000.000 


20.7364 


7.5478 


1350.88 


145220.12 


435 


189225.000 


82312875.000 


20.8567 


7.5770 


1366.59 


148616.97 


440 


193600.000 


85184000.000 


20.9762 


7.6059 


1382.30 


152053.08 


445 


198025.000 


88121125.000 


21.0950 


7.6346 


1398.01 


155528.47 


450 


202500.000 


91125000.000 


21.2132 


7.6631 


1413.72 


159043.13 


455 


207025.000 


94196375.000 


21.3307 


7.6914 


1429.42 


162597.05 


460 


211600.000 


97336000.000 


21.4476 


7.7194 


1445.13 


166190.25 


465 


216225.000 


100544625.000 


21.5639 


7.7473 


1460.84 


169822.72 


470 


220900.000 


103823000.000 


21.6795 


7.7750 


1476.55 


173494.45 


475 


225625.000 


107171875.000 


21.7945 


7.8025 


1492.26 


177205.46 


480 


280400.000 


110592000.000 


21.9089 


7.8297 


1507.96 


180955.74 


485 


235225.000 


114084125.000 


22.0227 


7.8568 


1523.67 


184745.28 


490 


240100.000 


117649000.000 


22.1359 


7.8837 


1539.38 


188574.10 


495 


245025.000 


121287375.000 


22.2486 


7.9105 


1555.09 


192442.18 


500 


250000.000 


125000000.000 


22.8607 


7.9370 


1570.80 


196349.54 



TABLE 2. 
Trigonometric Functions. 



Angle, 
degrees 


l^ine 


Tangent 




Angle, 
degrees 


Sine 


Tangent 




0.0 


0.00000 


0.00000 


90.0 


47.5 


0.73728 


1.0913 


42.5 


2.5 


0.04362 


0.04362 


87.5 


50.0 


0.76604 


1.1917 


40.0 


5.0 


0.08716 


0.08749 


85.0 


52.5 


0.79335 


1.3032 


87.5 


7.5 


0.13053 


0.13165 


82.5 


55.0 


0.81915 


1.4281 


85.0 


10.0 


0.17365 


0.17633 


80.0 


57.5 


0.84339 


1.5697 


82.5 


12.5 


0.21644 


0.22169 


77.5 


60.0 


0.86603 


1.7321 


80.0 


15.0 


0.25882 


0.26795 


75.0 


62.5 


0.88701 


1.9210 


27.5 


17.5 


0.30071 


0.31530 


72.5 


65.0 


0.90631 


2.1445 


25.0 


20.0 


0.34202 


0.36397 


70.0 


67.5 


0.92388 


2.4142 


22.5 


22.5 


0.38263 


0.41421 


67.5 


70.0 


0.93969 


2.7474 


20.0 


25.0 


0.42262 


0.46631 


65.0 


72.5 


0.95372 


8.1716 


17.5 


27.5 


0.46175 


0.52057 


62.5 


75.0 


0.96593 


3.7321 


15.0 


80.0 


0.50000 


0.57735 


60.0 


77.5 


0.97630 


4.5107 


12.5 


82.5 


0.53730 


0.63707 


57.5 


80.0 


0.98481 


5.6713 


10.0 


85.0 


0.57358 


0.70021 


55.0 


82.5 


0.99144 


7.5958 


7.5 


87.5 


0.60876 


0.76733 


52.5 


85.0 


0.99619 


11.430 


5.0 


40.0 


0.64279 


0.83910 


50.0 


87.0 


0.99863 


19.081 


3.0 


42.5 


0.67559 


0.91633 


47.5 


88.5 


0.99966 


38.188 


1.5 


45.0 


0.70711 


l.OOOO 


45.0 


90.0 


1.0000 


Infinite 


0.0 




Cosine 


Cotan- 
gent 


Angle, 
degrees 




Cosine 


Cotan- 
gent 


Angle, 
degrees 



1 lb. per sq. in. 



TABLE 3. 
Equivalents of Compound Units. 

r 27.71 in. of water at 62° F. 

I 2.0355 in. of mercury at 32" F, 

= ^ 2.0416 in. of mercury at 62° F, 

i 2.3090 ft. of water at 62^ F. 



■1784. 



ft. of air at 32° F. 



1 oz. per sq. in. 

1 in. of water at 62° F. 
1 in. of water at 32° F. 
1 in. of mercury at 62° F. 
1 ft. of air 



0.1276 in. of mercury at 62° F. 
1.732 in. of water at 62° F. 



I 0.03609 lb. or .5574 oz. per s. in. 
= -< 5.196 lbs. per sq. ft. 

( 0.0736 in. of mercury at 62° F. 

^ J 5.2021 lbs. per sq. ft. 
( 0.036125 lb. per sq. in. 

( 0.491 lb. or 7.86 oz. per sq. In. 
= 1.132 ft. of water at 62° F. 
(13.58 in. of water at 62° F. 



poo 



F. 



\ 0.0005606 lb. per sq. in. 

I 0.015534 in. of water at 62' 



F. 



334 



TABLE 4. 



Properties of Saturated Steam.* 



Absolute 


Tempera- 


Heat 


Heat of the 


Total 


press 're lbs. 


ture 


of the 


vaporiza- 


heat 


per sq. in. 


deg. F. 


liquid 


tion 1 


above 32° 


1 


101.84 


69.8 


1034.7 


1104.5 


2 


126.15 


94.2 


1021.9 


1116.1 


3 


141.52 


109.6 


1012.2 


1121.8 


4 


153.00 


121.0 


1005.5 


1126.5 


5 


162.26 


130.3 


1000.0 


1130.3 


6 


170.07 


138.1 


995.5 


1133.6 


7 


176.84 


144.9 


991.4 


1136.3 


8 


182.86 


150.9 


987.8 


1138.7 


9 


188.27 


156.4 


984.5 


1140.9 


10 


193.21 


161.3 


981.4 


1142.7 


11 


197.74 


165.9 


978.6 


1144.5 


12 


201.95 


170.1 


976.0 


1146.1 


13 


205.87 


174.1 


973.6 


1147.7 


14 


209.55 


177.8 


971.2 


1149.0 


14.7 


212.00 


180.3 


969.7 


1150.0 


15 


213.03 


181.3 


969.1 


1150.4 


■<6 


216.31 


184.6 


967.0 


1151.6 


17 


219.43 


187.8 


965.0 


1152.8 


18 


222.40 


190.8 


963.1 


1153.9 


19 


225.24 


193.7 


961.2 


1154.9 


20 


227.95 


196.4 


959.4 


1155.8 


21 


230.56 


199.1 


957.7 


1156.8 


22 


233.07 


201.6 


956.0 


1157.6 


23 


235.50 


204.1 


954.4 


1158.5 


24 


237.82 


206.4 


952.9 


1159.3 


25 


240.07 


208.7 


951.4 


1160.1 


26 


242.26 


210.9 


949.9 


1160.8 


27 


244.36 


213.0 


948.5 


1161. 5 


28 


246.41 


215.1 


947.1 


1162.2 


29 


248.41 


217.2 


945.8 


1163.0 


30 


250.34 


219.1 


944.4 


1163.5 


31 


252.22 


221.0 


943.1 


1164.1 


32 


254.05 


222.9 


941.8 


1164.7 


83 


255.84 


224.7 


940.6 


1165.3 


34 


257.59 


226.5 


939.4 


1165.9 


35 


259.29 


228.2 


9.38.2 


1166.4 


36 


260.96 


229.9 


937.1 


1167.0 


37 


262.58 


231.6 


935.9 


1167.5 


38 


264.17 


233.2 


934.8 


1168.0 


39 


265.73 


234.8 


933.7 


1168.5 


40 


267.26 


236.4 


932.6 


1169.0 


41 


268.76 


237.9 


931.6 


1169.5 


42 


270.23 


239.4 


930.6 


1170.0 


43 


271.66 


240.8 


929.5 


1170.3 


44 


273.07 


242.3 


928.5 


1170.8 



Condensed from Peabody's Steam Tables. 1911 Edition. 

335 



Absolute 


Tempera- 


Heat 


Heat of the 


Total 


pressure lbs. 


ture 


of the 


vaporiza- 


heat 


per sq. in. 


deg. F. 


liquid 


tion 


above 32° 


45 


274.46 


243.7 


927.5 


1171.2 


46 


275.82 


245.1 


920.6 


1171.7 


47 


277.16 


246.4 


925.6 


1172.0 


48 


278.47 


247.8 


924.7 


1172.5 


49 


279.76 


249.1 


923.8 


1172.9 


50 


281.03 


250.4 


922.8 


1173.2 


51 


282.28 


251.7 


921.9 


1173.6 


52 


283.52 


253.0 


921.0 


1174.0 


53 


284.74 


254.2 


920.1 


1174.3 


54 


285.93 


255.4 


919.3 


1174.7 


55 


287.09 


256.6 


918.4 


. 1175.0 


56 


288.25 


257.8 


917.6 


1175.4 


57 


289.40 


259.0 


916.7 


1175.7 


58 


290.53 


260.1 


915.9 


1176.0 


59 


291.64 


261.3 


915.1 


1176.4 


60 


292.74 


262.4 


914.3 


1176.7 


61 


293.82 


263.5 


913.5 


1177. C 


62 


294.88 


264.6 


912.7 


1177.3 


63 


295.93 


265.7 


911.9 


1177.6 


64 


296.97 


266.7 


911.1 


1177.8 


65 


298.00 


267.8 


910.4 


1178.2 


66 


299.02 


268.8 


909.6 


1178.4 


67 


300.02 


269.8 


908.9 


1178.7 


68 


301.01 


270.9 


908.1 


1179.0 


69 


301.99 


271.9 


907.4 


1179.3 


70 


802.96 


272.9 


906.6 


1179.5 


71 


303.91 


273.8 


905.9 


1179.7 


72 


304.86 


274.8 


905.2 


1180.0 


73 


305.79 


275.8 


904.5 


1180.3 


74 


306.72 


276.7 


903.8 


1180.5 


75 


307.64 


277.7 


903.1 


1180.8 


76 


308.54 


278.6 


902.4 


1181.0 


77 


309.44 


279.5 


901.8 


1181.3 


78 


310.33 


280.4 


901.1 


1181.5 


79 


311.21 


281.3 


900.4 


1181.7 


80 


312.08 


282.2 


899.8 


1182.0 


81 


312.94 


283.1 


899.1 


1182.2 


82 


313.79 


283.9 


898.5 


1182.4 


83 


314.63 


284.8 


897.8 


1182 6 


84 


815.47 


285.7 


897.2 


1182.9 


85 


316.30 


286.5 


896.6 


1183.1 


86 


317.12 


287.4 


895.9 


1183.3 


87 


317.93 


288.2 


895.3 


1183.5 


88 


318.73 


289.0 


894.7 


1183.7 


89 


319.53 


289.9 


894.1 


1184.0 


90 


820.32 


290.7 


893.5 


1184.2 


91 


321.10 


291.5 


892.9 


1184.4 


92 


321.88 


292.3 


892.3 


1184.6 


93 


822.65 


293.1 


891.7 


1184.8 


94 


323.41 


293.9 


891.1 


1185.0 



:3G 



Absolute 


Tempera- 


Heat 


Heat of the 


Total 


press're lbs. 


ture 


of the 


vaporiza- 


heat 


per sq. in. 


deg. F. 


liquid 


tion 


Above 32« 


95 


324.16 


294.6 


890.5 


1185.1 


96 


324.91 


295.4 


889.9 


1185.3 


97 


325.66 


296.2 


889.3 


1185.5 


98 


326.40 


296.9 


888.7 


1185.6 


99 


327.13 


297.7 


888.2 


1185.9 


100 


327.86 


298.5 


887.6 


1186.1 


101 


828.58 


299.2 


887. 


1186.2 


102 


329.30 


299.9 


886.5 


1186.4 


103 


330.01 


300.6 


8S5.9 


1186.5 


101 


330.72 


301.4 


885.3 


1186.7 


105 


331.42 


302.1 


884.8 


1186.9 


106 


332.11 


302.8 


884.3 


1187.1 


107 


332.79 


803.5 


883.7 


1187.2 


108 


333.48 


304.2 


883.2 


1187.4 


109 


334.16 


804.9 


882.6 


1187.6 


110 


334.83 


305.6 


882.1 


1187.7 


111 


335.50 


306.3 


881.6 


1187.9 


112 


836.17 


307.0 


881.0 


1188.0 


113 


336.83 


807.7 


880.5 


1188.2 


114 


337.48 


308.3 


880.0 


1188.3 


115 


338.14 


309.0 


879.5 


1188.5 


116 


338.78 


309.7 


879.0 


1188.7 


117 


339.42 


310.3 


878.5 


1188.8 


118 


340.06 


311.0 


878.0 


1189.0 


119 


840.69 


811.7 


877.4 


1189.1 


120 


341.31 


312.3 


876.9 


1189.2 


121 


341.94 


312.9 


876.4 


1189.3 


122 


842.56 


313.6 


875.9 


1189.5 


123 


843.18 


314.2 


875.4 


1189.6 


124 


343.79 


814.8 


875.0 


1189.8 


125 


844.39 


815.5 


874.5 


1190.0 


126 


345.00 


316.1 


874.0 


1190.1 


127 


845.60 


316.7 


873.5 


1190.2 


128 


846.20 


317.3 


873.0 


1190.3 


129 


846.79 


317.9 


872.6 


1190.5 


130 


847.38 


818.6 


872.1 


1190.7 


131 


847.96 


319.2 


871.6 


1190.8 


132 


348.55 


319.8 


871.1 


1190.9 


133 


349.13 


320.4 


870.7 


1191.1 


134 


849.70 


820.9 


870.2 


1191.1 


135 


350.27 


321.5 


869.8 


1191.3 


136 


850.84 


322.1 


869.3 


1191.4 


137 


851.41 


322.7 


868.8 


1191.5 


138 


851.98 


323.3 


868.3 


1191.6 


139 


352.54 


323.9 


867.9 


1191.8 


140 


353.00 


824.4 


867.4 


1191.8 


141 


853.65 


825.0 


867.0 


1192.0 


142 


854.20 


325.6 


866. 5 


1192.1 


143 


354.75 


326.2 


866.1 


1192.3 


144 


355.29 


326.7 


865.6 


1192.3 



337 



TABLE 5. 



Naperian LiOgarithms. 

2.7182818 Log e = 0.4342945 



= M. 



1.0 


0.0000 


4.1 


1.4110 


7.2 


1.9741 


1.1 


0.0953 


4.2 


1.4351 


7.3 


1.9879 


1.3 


0.1823 


4.3 


1.4586 


7.4 


2.0015 


1.3 


0.2624 


4.4 


1.4816 


7.5 


2.0149 


1.4 


0.3365 


4.5 


1.5041 


7.6 


2.0281 


1.5 


0.4055 


4.6 


1.5261 


7.7 


2.0412 


1.6 


0.4700 


4.7 


1.5476 


7.8 


2.0541 


1.7 


0.5306 


4.8 


1.5686 


7.9 


2.0669 


1.8 


0.5878 


4.9 


1.5892 


8.0 


2.0794 


1.9 


0.6419 


5.0 


1.6094 


8.1 


2.0919 


2.0 


0.6931 


5.1 


1.6292 


8.2 


2.1041 


2.1 


0.7419 


5.2 


1.6487 


8.3 


2.1163 


2.2 


0.7885 


5.3 


1.6677 


8.4 


2.1282 


2.3 


0.8329 


5.4 


1.6864 


8.5 


2.1401 


2.4 


0.8755 


5.5 


1.7047 


8.6 


2.1518 


2.5 


0.9163 


5.6 


1 .7228 


8.7 


2.1633 


2.6 


0.9555 


6.7 


1.7405 


8.8 


2.1748 


2.7 


0.9933 


5.8 


1.7579 


8.9 


2.1861 


2.8 


1.0296 


6.9 


1.7750 


9.0 


2.1972 


2.9 


1.0647 


6.0 


1.7918 


9.1 


2.2083 


S.O 


1.0986 


6.1 


1.8083 


9.2 


2.2192 


8.1 


1.1312 


6.2 


1.8245 


9.3 


2.2300 


S.2 


1.1632 


6.3 


1.8405 


9.4 


2.2407 


8.3 


1.1939 


6.4 


1.8563 


9.5 


2.2513 


8.4 


1.2238 


6.5 


1.8718 


9.6 


2.2618 


8.5 


1.2528 


6.6 


1.8871 


9.7 


2.2721 


8.6 


1.2809 


6.7 


1.9021 


9.8 


2.2824 


8.7 


1.3083 


6.8 


1.9169 


9.9 


2.2925 


S.S 


1.3350 


6.9 


1.9315 


10.0 


2.3026 


8.9 


1.3610 


7.0 


1.9459 






4.0 


1.3863 


! 7.1 


1.9601 







TABLE 6. 
Water Conversion Factors.* 



U. S. gallons 

U. S. gallons 

U. S. gallons 

U. S. gallons 

Cubic inches of water (39.1°) 

Cubic inches of water (39.1°) 

Cubic inches of water (39.1°) 

Cubic feet of water (39.1°) 

Cubic feet of water (39.1°) 

Cubic feet of water (39.1°) 
Pounds of water 

Pounds of water 

Pounds of water 



X 


8.33 


= pounds. 


X 


0.13368 


= cubic feet. 


X 231.00000 


= cubic inches. 


X 


3.78 


= liters. 


X 


0.036024 


= pounds. 


X 


0.004329 


= U. S. gallons 


X 


0.576384 


= ounces. 


X 


62.425 


= pounds. 


X 


7.48 


= U. S. gallons 


X 


0.028 


= tons. 


X 


27.72 


= cubic inches. 


X 


0.01602 


= cubic feet. 


X 


0.12 


= U. S. gallons 



^American Machinist Hand Book. 

338 



TABLE 7. 

Volume and AVeight of Dry Air at Different Temperatures.* 

Under a constant atmospheric pressure of 29.92 inches of 
mercury, the volume at 32° F. being 1. 



Temp, 
deg. F. 



Volume 



Weight 
per eu. ft. 



Temp, 
deg. F. 



Volume 



Weight 
per cu . f t , 






.935 


.0864 


500 


1.954 


.0413 


13 


.960 


.0843 


552 


2.056 


.0385 


22 


.980 


.0824 


600 


2.150 


.0376 


32 


1.000 


.0807 


650 


2.250 


.0357 


42 


1.020 


.0791 


700 


3.363 


.0338 


52 


1.041 


.0776 


750 


2.465 


.0828 


62 


1.061 


.0761 i 


800 


2.566 


.0315 


72 


1.083 


.0747 


850' 


2.668 


.0303 


82 


1.103 


.0733 


900 


2.770 


.0292 


93 


1.123 


.0720 


950 


2.871 


.0281 


103 


1.143 


.0707 


lOOO 


2.974 


.0268 


113 


1.163 


.0694 


1100 


3.177 


.0254 


122 


1.184 


.0G82 


1200 


3.381 


.0239 


183 


1.204 


.0671 


130O 


3.584 


.0225 


142 


1.224 


.0659 


140O 


3.788 


.0313 


153 


1.245 


.0649 


1500 


3.993 


.0203 


163 


1.265 


.0638 


1600 


4.196 


.0193 


173 


1.2S5 


.0628 


! 170O 


4.403 


.0183 


183 


1.306 


.C618 


180O 


4.605 


.0175 


193 


1.326 


.0609 


1900 


4.808 


.0168 


203 


1.847 


.0600 


2000 


5.013 


.0161 


213 


1.867 


.0591 


2100 


5.217 


.0155 


230 


1.404 


.0575 


22CO 


5.420 


.0149 


250 


1.444 


.0559 


230O 


5.625 


.0143 


275 


1.495 


.0540 


240O 


5.827 


.0138 


300 


1.546 


.0523 


2500' 


6.033 


.0133 


325 


1.597 


.0506 


2600 


6.236 


.0130 


350 


1.648 


.0490 


2700 


6.440 


.0125 


375 


1.689 


.0477 


1 2800 


6.644 


.0121 


400 


1.750 


.0461 


2900 


6.847 


.0118 


450 


1.853 


.0436 


30OO 


7.051 


.0114 



Suplee's M. E. Reference Book. 



339 



TTABLE 8. 

Weight of PuTe Water per Cubic Foot at Various 
Temperatures.* 



Temp. 


Weight 


B. t. u. 


Temp. 


Weight 


B. t. u. 


deg. 


lbs. per 


per pound 


deg. 


lbs. per 


per pound 


F. 


cu. ft. 


above 32 


F. 


eu. ft. 


above 82 


32 


62.42 


0.00 


77 


62.26 


4^.04 


. 83 


62.42 


1.01 


78 


62.25 


46.04 


84 


62.42 


2.02 


79 


62.24 


47.04 


85 


62.42 


3.02 


80 


62.23 


48.03 


86 


62.42 


4.03 


81 


62.22 


49.03 


87 


62.42 


5.04 


82 


62.21 


50.03 


38 


62.42 


6.04 


83 


62.20 


51.02 


89 


.62.42 


7.05 


84 


62.19 


52.02 


40 


62.42 


8.05 


85 


62.18 


58.02 


41 


62.42 


9.05 


86 


62.17 


54.01 


42 


62.42 


10.06 


87 


62.16 


55.01 


43 


62.42 


11.06 


88 


62.15 


56.01 


44 


62.42 


12.06 


89 


62.14 


57.00 


45 


62.42 


13.07 


90 


62.13 


58.00 


46 


62.42 


14.07 


91 


62.12 


59.00 


47 


62.42 


15.07 


92 


62.11 


60.00 


48 


62.41 


16.07 


93 


62.10 


60.99 


49 


62.41 


17.08 


94 


62.09 


61.99 


50 


62.41 


18.08 


95 


62.08 


62.99 


51 


62.41 


19.08 


96 


62.07 


63.98 


52 


62.40 


20.08 


97 


62.06 


64.98 


53 


62.40 


21.08 


98 


62.05 


65.98 


54 


62.40 


22.08 


99 


62.03 


66.97 


55 


62.39 


23.08 


100 


62.02 


67.97 


56 


62.39 


24.08 


101 


62.01 


68.97 


57 


62.39 


25.03 


102 


62.00 


69.96 


58 


62.38 


26.08 


103 


61.99 


70.96 


59 


62 -.38 


27.08 


104 


61.97 


71.96 


60 


62.37 


28.08 


105 


61.96 


72.95 


61 


62.37 


29.08 


106 


61.95 


73.95 


62 


62.36 


30.08 


107 


61.93 


74.95 


68 


62.36 


31.07 


108 


61.92 


75.95 


64 


62.35 


32.07 


109 


61.91 


76.94 


65 


62.34 


33.07 


110 


61.89 


77.94 


66 


62.34 


34.07 


111 


61.88 


78.94 


67 


62.33 


35.07 


112 


61.86 


79.93 


68 


62.33 


36.07 


113 


61.85 


80.93 


69 


62.32 


37.06 


114 


61.83 


81.93 


70 


62.31 


38.06 


115 


61.82 


82.92 


71 


62.31 


39.06 


116 


61.80 


83.92 


72 


62.30 


40.05 


117 


61.78 


84.92 


78 


62.29 


41.05 


118 


61.77 


85.92 


74 


62.28 


42.05 


119 


61.75 


86.91 


75 


62.28 


43.05 


120 


61.74 


87.91 


76 


62.27 


44.04 


121 


61.72 


88.91 



^Kent's M. E. Pocket-Book. 8th Edition. 



340 



Temp. 


Weight 


B. t. u. 


Temp. 


Weight 


B. t. u. 


deg. 


lbs. per 


per pound 


deg. 


lbs. per 


per pound 


F. 


eu. ft. 


above S2 


P. 


cu. ft. 


above 32 


122 


61.70 


89.91 


167 


60.83 


134.86 


123 


61.68 


90.90 


168 


60.81 


135.86 


124 


61.67 


91.90 


169 


60.79 


136.86 


125 


61.65 


92.90 


170 


60.77 


137.87 


126 


61.63 


93.90 


171 


60.75 


138.87 


127 


61.61 


94.89 


172 


60.73 


139.87 


128 


61.60 


95.89 


173 


60.70 


140.87 


129 


61.58 


96.89 


174 


60.68 


141.87 


130 


61.56 


97.89 


175 


60.66 


142.87 


181 


61.54 


98.89 


176 


60.64 


143.87 


132 


61.52 


99.88 


177 


60.62 


144.88 


133 


61.51 


100.88 


178 


60.59 


145.88 


134 


61.49 


101.88 


179 


60.57 


146.88 


135 


61.47 


102.88 


180 


60.55 


147.88 


136 


61.45 


103.88 


181 


60.53 


148.88 


137 


61.43 


104.87 


182 


60.50 


149.89 


138 


61.41 


105.87 


183 


60.48 


150.89 


139 


61.39 


106.87 


184 


60.46 


151.89 


140 


61.37 


107.87 


185 


60.44 


152.89 


141 


61.36 


108.87 


186 


60.41 


153.89 


142 


61.34 


109.87 


187 


60.39 


154.90 


143 


61.32 


110.87 


188 


60.37 


155.90 


144 


61.30 


111.87 


189 


60.34 


156.90 


145 


61.28 


112.86 


190 


60.32 


157.91 


146 


61.26 


113.86 


191 


60.29 


158.91 


147 


61.24 


114.86 


192 


60.27 


159.91 


148 


61.22 


115.86 


193 


60.25 


160.91 


149 


61.20 


116.86 


194 


60.22 


161.92 


150 


61.18 


117.88 


195 


60.20 


162.92 


151 


61.16 


118.86 


196 


60.17 


163.92 


152 


61.14 


119.86 


197 


60.15 


164.93 


153 


61.12 


120.80 


198 


60.12 


165.93 


154 


61.10 


121.86 


199 


60.10 


166.94 


155 


61.08 


122.86 


200 


60.07 


167.94 


156 


61.06 


123.86 


201 


60.05 


168.94 


157 


61.04 


124.86 


202 


60.02 


169.95 


158 


61.02 


125.86 


203 


60.00 


170.95 


159 


61.00 


126.86 


204 


59.97 


171.96 


160 


60.98 


127.86 


205 


59.95 


172.96 


161 


60.96 


128.86 


206 


59.92 


173.97 


162 


60.94 


129.86 


207 


59.89 


174.97 


163 


60.92 


130.86 


208 


5'J.87 


175.98 


164 


60.90 


131.86 


209 


59.84 


176.98 


165 


60.87 


132.86 


210 


59.82 


177.99 


166 


60.85 


133.86 


211 


59.79 


178.99 








212 


59.76 


180. 



11 



TABLE 9. 
Boiling Point of AVater at Different Heighti^ of Vacuum. 





Height of 




Height of 


Temp. 


mercury m 


Tem.p. 


mercury m 


F, 


vacuum tube 


F. 


vacuum tube 




in inches 




in inches 


212.0 


0.00 


175.8 


16.00 


210.3 


1.00 


172.6 


17.00 


208.5 


2.00 


169.0 


18.00 


206.8 


3.00 


165.3 


19.00 


204.8 


4.00 


161.2 


20.00 


202.9 


5.00 


156.7 


21.00 


200.9 


6.00 


151.9 


22.00 


199.0 


7.00 


146.5 


23.00 


196.7 


8.00 


140.3 


24.00 


194.5 


9.00 


133.3 


25.00 


192.2 


10.00 


124.9 


26.00 


189.7 


11.00 


114.4 


27.00 


187.3 


12.00 


108.4 


28.00 


184.6 


13.00 


102.0 


29.00 


181.3 


14.00 


98.0 


29.92 


178.9 


15.00 







TABLE 10. 

Weiglit of Water TKith. Air per Cubic Foot at Different 

Temperatures and at Saturation. 



^ 




^ 




^ 




Ph 


»> 


1 ^' 




^ 






■4J 




-M 




-M 




-M 




-M 




•tj 


ft 








d 
§ 








d 
S 




d 

a 




s 




H 


^a 


S 


^ fci 


H 


^U 


S 


^ bi 


S 


^a 


—20 


0.166 


2 


0.529 


24 


1.483 


46 


3.539 


68 


7.480 


90 


14.790 


—19 


0.174 


3 


0.554 


25 


1.551 


47 


3.667 


69 


7.726 


91 


15.234 


—18 


0.184 


4 


0..582 


26 


1.623 


48 


3,800 


70 


7.980 


92 


15.689 


—17 


0.196 


5 


0.610 


27 


1.697 


49 


3.936 


71 


8.240 


93 


16.155 


—16 


0.207 


6 


0.639 


28 


1.773 


50 


4.076 


72 


8.508 


94 


16.634 


—15 


0.218 


7 


0.671 


29 


1.853 


51 


4.222 


73 


8.782 


95 


17.124 


—14 


0.231 


8 


0.704 


30 


1.935 


52 


4.372 


74 


9.066 


96 


17.626 


—13 


0.243 


9 


0.739 


31 


2.022 


53 


4.526 


75 


9.856 


97 


18.142 


—12 


0.257 


10. 


0.776 


32 


2.113 


54 


4.685 


76 


9.655 


98 


18.671 


—11 


0.270 


11 


0.816 


33 


2.194 


55 


4.849 


77 


9.962 


99 


19.212 


—10 


0.285 


12 


0.856 


34 


2.279 


56 


5.016 


78 


10.277 


100 


19.766 


— 9 


0.300 


13 


0.898 


35 


2.366 


57 


5.191 


79 


10.601 


101 


20.335 


— 8 


0.316 


14 


0.941 


36 


2.457 


58 


5.370 


80 


10.934 


102 


21.017 


— 7 


0.332 


15 


0.986 


37 


2.550 


59 


5.555 


81 


11.275 


103 


21.514 


— 6 


0.350 


16 


1.032 


38 


2.646 


60 


5.745 


82 


11.626 


104 


22.125 


— 5 


0.370 


17 


1.080 


39 


2.746 


61 


5.941 


83 


11.987 


105 


22.750 


— 4 


0.389 


18 


1.128 


40 


2.849 


62 


6.142 


84 


12.336 


106 


23.392 


— 3 


0.411 


19 


1.181 


41 


2.955 


63 


6.349 


85 


12.786 


107 


24.048 


— 2 


0.434 


20 


1.235 


42 


8.064 


64 


6.563 


86 


13.127 


108 


24.720 


— 1 


0.457 


21 


1.294 


43 


3.177 


65 


6.782 


87 


13.526 


109 


25.408 





0.481 


22 


1.355 


44 


3.294 


66 


7.009 


88 


13.937 


110 


26.112 


1 


0.505 


23 


1.418 


45 


3.414 


67 


7.241 


89 


14.359 







3 42 



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343 



TABLE 12. 

Properties of Air y\itli Moisture under Pressure of One 

Atniospliere.* 







;-, 


. 








OJ OJ 


tJ 




<v o 




•11 ,^ 


Mixtures of air sfi 
with vapor 


turated 




O) 




c 




c9 
c 5d 










a 


'S 


cj O O 


Weight of cubic 
foot of the 




s 






r— • O 






jidxtij re . 


o 






"5=3 


^ 


o 


. 




■M 


as 

p 
es 

1 


.bos 

. ^ r-" 




o o 

M O 

3S 


a M i; 


-a . 
1-3 


xn 

-M O 

O fl 

sz u 

b£ O 




u 

t 

a 

O 

o 

Wed 


ft 

Si 


■S=,E 


to 


1 


2 


3 


4 


5 


6 


7 


8 


9 


10 


11 


12 





.935 


.0864 


0.044 


29.877 


.0863 


.000079 


.086379 


.00092 


1092.40 




48.5 


12 


.960 


.0842 


0.074 


29.849 


.0840 


.000130 


.084130 


.00115 


646.10 





50.1 


22 


.980 


.0824 


0.118 


29.803 


.0821 


.000202 


.082302 


.00245 


406.40 





51.1 


82 


1.000 


.0807 


0.181 


29.740 


.0802 


.000304 


.080504 


.00379 


263.81 


3289.0 


52.0 


42 


1.020 


.0791 


.0267 


29.654 


.0784 


.000440 


.078840 


.00561 


178.18 


2252.0 


53.2 


52 


1.041 


.0766 


0.388 


29.533 


.0766 


.000627 


.077227 


.00819 


122.17 


1595.0 


54.0 


60 


1.057 


.0764 


0.522 


29.390 


.0751 


.tX)O830 


.075252 


.01251 


92.27 


1227.0 


55.0 


62 


1.061 


.0761 


0.556 


29.365 


.0747 


.000881 


.075581 


.01179 


84.79 


1135.0 


55.2 


70 


1.078 


.0750 


0.754 


29.182 


.0731 


.001153 


.073509 


.01780 


64.59 


882.0 


56.2 


V2 


1.082 


.0747 


0.785 


29.136 


.0727 


.001221 


.073921 


.01680 


59.54 


819.0 


56.3 


82 


1.102 


.0733 


1.092 


28.829 


.0706 


.001667 


.072267 


.02361 


42.35 


600.0 


57.2 


92 


1.122 


.0720 


1.501 


28.420 


.0684 


.002250 


.070717 


.03289 


30.40 


444.0 


-o8A 


100 


1.139 


.0710 


1.929 


27.992 


.0664 


.002848 


.069261 


.04495 


23.66 


356.0 


59.1 


102 


1.143 


.0707 


2.036 


27.885 


.0659 


.002997 


.068897 


.04547 


21.98 


334.0 


59.5 


112 


1.163 


.0694 


2.731 


27.190 


.0631 


.003946 


.067042 


.06253 


15.99 


253.0 


60.6 


122 


1.184 


.0682 


3.621 


26.300 


.0599 


.005142 


.065046 


.08584 


11.65 


194.0 


61.7 


132 


1.204 


.0671 


4.752 


25.169 


.Oi64 


.006639 


.063039 


.11771 


8.49 


151.0 


62.5 


142 


1.224 


.0660 


6,165 


23.756 


.0524 


.008473 


.060873 


.16170 


6.18 


118.0 


63.7 


152 


1.245 


.0649 


7.930 


21.991 


.0477 


.010716 


.058416 


.22465 


4.45 


93.3 


64.7 


162 


1.265 


.0638 


10.099 


19.822 


.0423 


.013415 


.055715 


.31713 


3.15 


74.5 


65.8 


172 


1.285 


.0628 


12.758 


17.163 


.0360 


.016682 


.052682 


.46338 


2.16 


59.2 


66.9 


182 


1.306 


.0618 


15.960 


13.961 


.0288 


.020536 


.049336 


.71300 


1.402 


48.6 


68.0 


192 


1.326 


.0609 


19.828 


10.093 


.0205 


.025142 


.045642 


1.22643 


.815 


39.8 


69.0 


202 


1.347 


.0600 


24.450 


5.471 


.0109 


.030545 


.041445 


2.80230 
In- 
finite 


.357 


32.7 


70.0 


212 


1.367 


.0591 


29.921 


0.000 


.0000 


.036820 


.036820 


.000 


27.1 


71.1 



^Carpenter's H. & V. B. and Sturtevant's Mech. Draft. 



344 



TABLE 13. 
Dew-points of Air According to Its Hygrrometrte State.* 





1 


Relative moisture 


Teniu. 














' 








90% 


80% 


V0% 


60% 


50% 


C. 


F. 


C. 


F. 


C. 


F. 


C. 


F. 


C. 


F. 


C. 


F. 





32.0 


— 1.5 


29.3 


— 3.0 


26.6 


— 4.9 


23.2 


— 6.5 


20.3 


-9.2 


15.4 


2 


35.6 


0.0 


33.6 


— 0.9 


30.4 


— 2.5 


27.5 


— 4.8 


23.4 


— 7.1 


19.2 


4 


39.2 


2.4 


36.3 


0.9 


33.6 


— 0.9 


.30.4 


— 2.9 


26.8 


— 5.3 


22.5 


6 


42.8 


4.5 


40.1 


2.9 


37.2 


0.9 


33.6 


— 1.3 


29.7 


— 3.7 


25.3 


8 


46.4 


6.4 


43.5 


4.5 


40.1 


2.7 


36.9 


0.6 


33.1 


— 1.9 


28.6 


10 


50.0 


8.5 


47.3 


0.8 


41.2 


4.5 


40.1 


2.5 


36.5 


0.0 


32.0 


12 


53.6 


10.5 


50.9 


8.5 


47.3 


6.8 


44.2 


4.3 


.39.7 


2.0 


35.6 


14 


57.2 


12.3 


54.1 


10.5 


50.9 


8.5 


47.3 


6.2 


43.2 


3.7 


38.7 


16 


60.8 


14.4 


57.9 


12.6 


54.7 


10.5 


50.9 


8.3 


46.9 


5.6 


42.1 


18 


64.4 


16.5 


61.7 


14.6 


58.3 


12.4 


54.3 


10.0 


50.0 


7.4 


45.3 


20 


68.0 


18.3 


64.9 


16.5 


61.7 


14.4 


57.9 


11.9 


53.4 


9.2 


48.6 


22 


71.6 


20.3 


68.5 


18.4 


65.1 


16.3 


61.3 


13.7 


56.7 


11.6 


52.8 


24 


75.2 


22.2 


72.1 


20.5 


68.9 


18.4 


65.1 


15.6 


60.0 


13.0 


55.4 


26 


78.8 


24.4 


75.9 


22.2 


72.1 


20.1 


68.2 


17.6 


63.6 


14.7 


58.5 


28 


82.4 


26.3 


79.3 


24.2 


75.6 


22.0 


71.6 


19.5 


67.1 


17.5 


63.5 


30 


86.0 


28.3 


82.9 


26.3 


79.3 


23.9 


75.0 


21.5 


70.7 


18.3 


64.9 




♦Bulletin 21, Int. Ass'n of Refrig. 

Psychrometric Charts Recent Tests. 

In recent years a highly technical study of humidity 
and its con-trol has been made by Mr. Willis H. Carrier. Fig. 
A shows, merely for the sake of comparison, how closely his 

results checked the earlier 
values obtained by the Gov- 
ernment Weather Bureau. The 
following charts, Figs. B and 
C, summarize the results of 
Mr. Carrier's experiments. 
onvBuLB- - - Fig. C is a part of Fig. B 

Fig. A. drawn to a larger scale. 

As one illustration of the use of the chart, refer to Fig 
C with air at 40 degrees and 40 per cent, humidity. If this 
air be heated to 100 degrees without addition of moisture 
it will be seen by interpolation that the humidi-ty drops 
to about 8 per cent. If the same be heated to 100 degrees 
and enough moisture be added to keep the relative humid- 
ity at 40 per cen-t., then the absolute humidity c-hanges from 
15 grains to 120 grains per pound of air. The.se figures 
may be reduced to grains per cubic foot by dividing by the 
volume per pound as given in the second column and will 
be found to check closely with those given by Fig. 7 and 
Table 9. Almost any odher points relating to changes in 
volume, humidity and contained heat may be easily worked 
out by these curves. oir: 




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^^mMmimi} 


-s! 






• 


























\ 


\ 




u 


\ 




— 1 


wmw 


































\ 




''^\ 




\ 




1 


WM/% 


5f 


































~\ 




% 


\ 


\ 




1 


mm^/ 


^ 


































^\ 




^ 


A 


\ 




wMkr 




~1 








>o, 


2JPUJ 


P C5 


l,OU, 


■' ^J' 


Kt^C. 


^ 










o 




' 


i\\ 




\ 




wmvi'' 






w;o< 


•^ 

^^i 


>p3(t 


vn/ft 


Mi 


^1 ' 5i 


«^ 


pOJi 


►^ 


P/a* 






\ o 




4\ 




\ 




\mM 


!S< 




s 


vnjs 


oum 


'MfJi 




iWH, 




KJfJ 


<,faj 


,*§ 




•G 








A 


\>, 


■ ^ 




mm 




§ 




o 




1 




^ 


VlJdS, 






% 




5 




^ 






§ 


\^ 






if 


w 


•G 






« 
& 


L 




J 


4 




E^ 


^ 
^ 


J 


4 




J 






-^ 


— 


-W 


\ 


I 


m 


^ 



s 

o 
u 



^ o 






347 



TABLE 14. 
Fuel Value of American Coals.* 



Coal 
Name or locality- 



Fuel value per pound 
of coal. 






•MO 



IS"* 



ARKANSAS. 

Spadra, Johnson Co 

Coal Hill, Johnson Co 

Huntington Co. 

Lignite 

COLORADO. 

Lignite 

Lignite, slack 

ILLINOIS. 

Big Muddy, Jackson Co 

Colchester, Slack 

Gillespie, Macoupin Co 

Mercer Co. 

INDIANA. 

Block 

Cannel 

IOWA. 

Good cheer 

KENTUCKY. 

Caking 

Cannel 

Lignite 

MISSOURI. 

Bevler Mines 

NEW MEXICO. 

Coal 

OHIO. 
Briar Hill, Mahoning Co.-. 

Hocking Valley 

PENNSYLVANIA. 

Anthracite 

Anthracite, pea 

Pittsburgh (average) 

Youghiogheney 

TEXAS. 

Fort Worth 

Lignite 

WEST VIRGINIA 

Pocahontas 

New River 



14,420 



9,215 

13,500 
8,500 



14,020 
13,097 



14,391 

15,198 

9,326 



13,714 
13,414 

14,199 
12,300 



12,962 
14,200 



11,812 
11,756 



11,781 
9,035 
9,739 

13,123 



8,702 



9,890 
11,756 



13,104 
12,936 

9,450 
14,273 



14.90 

12.22 

12.17 

9.54 

14.04 
8.83 

12.19 

9.35 

10.09 

13.58 

14.50 
13.56 

9.01 

14.89 

16.76 

9.65 

10.24 

12.17 

14.20 
13.90 

14.70 
12.73 
13.46 
13.39 

9.78 
13.41 

14.71 
14.70 



*Sturtevant's "Mechanical Draft." 



348 



TABLE 15. 
Capacities of Cliimneys.* 






Maximum sq. ft. of cast iron radiating 

surface and B. t. u. for a flue of the 

given diameter and height 



^ 


rC 


^ 


^ 


bo 


bo 


to 


bX) 










^ 


r^ 


r^ 


rfl 


, 


, 


, 


. 




-tJ 


+3 


+a 


H-i 


^M 


tH 


"r-i 


o 


c:» 


-<:+< 


rH 


00 


^ 


^ 


00 



bfl 

4^ 



10 



12 



15 



18 



Steam 

Hot water 
B. t. u. ._. 

Steam 

Hot water 
B. t. u. ._. 

Steam 

Hot water 
B. t. u. __. 

Steam 

Hot water 
B. t. u. ._ 

Steam __, 
Hot water 
B. t. u. _. 

Steam ___ 
Hot water 
B. t. u. ._ 

Steam 

Hot water 
B. t. u. __ 

Steam .__ 
Hot water 
B. t. u. __ 



146 

243 

36500 

228 

379 

57000 

327 

544 
81750 

445 

742 

111250 

582 

969 

145500 

909 

1514 

227250 

1537 

2561 

384250 

2327 

3878 
581750 



175 

291 
43750 


204 

840 

51000 


233 

388 

58250 


262 

437 

65500 


273 

455 

68250 


319 

531 

79750 


364 

607 

91000 


410 

683 

102500 


392 

653 

98000 


457 

762 

114250 


523 

871 
130750 


588 

980 

147000 


534 

890 

133500 


623 

1038 

155750 


712 

1187 

178000 


801 

1335 

200250 


698 

1163 

174500 


814 

1357 

203500 


930 

1551 

232500 


1047 

1745 

261750 


109O 

1817 

272500 


1272 

2120 
318000 


1454 

2423 

363500 


1636 

2726 

409000 


1844 

3073 

461000 


2151 

8586 

537750 


2458 

4098 

614500 


2766 

4610 

691500 


2792 

4653 

698000 


3257 

5429 

814250 


8722 

6204 

930500 


4188 

6980 

1047000 



291 

485 

72750 

455 

758 

113750 

653 

1083 
163250 

890 

1483 

222500 

1163 

1938 
290750 

1817 

3028 
454250 

3073 

5122 

768250 

4653 

7755 
1163250 



Radiation is calculated at 250 B. t. u. steam, 150 B. t. u. water. 
*Th0 Model Boiler Manual. 



349 



TABLE 16. 
E^qiialization of Smoke Flues — Commercial Sizes.* 



Inside 
diameter 
lined flue 



Brick flue 
not lined 
well built 



Rectangular 

lined flue 

outside of tile 



Outside 
iron 
stack 



6 


SVzxSVz 




8 


7 


8y2xsvo 


7x7 


9 


8 


8y2x8V2 


8^^x81/2 


10 


9 


872X13 


SUxlS 


11 


10 


81/^x13 


8HX13 


13 


13 


13x13 


13x13 


14 


15 


13x17 


13x18 


17 


18 


17x211/:. 


18x18 


20 



Round flue tile lining is listed by its inside measurement. 
Rectangular lining by outside measurement. 

TABLE 17. 
Dimensions of Registers.* 





Nominal 


Effective 






Size of 


area cf 


area of 




Extreme 


opening, 
inches 


opening, 
square 


opening, 
square 


Tin box size, 
inches 


dimensions of 

register face, 

inches 




Inches 


inches 




6x10 


CO 


40 


6i^B X lOi^e 


7H x llli 


8 X 10 


80 


53 


8H X lOH 


9H X IVA 


8x12 


96 


64 


8H X 12H 


9K X rsH 


8x15 


120 


80 


8H X 15V& 


9H X 16li 


9x12 


108 


72 


9il X 12H 


107^ X 13^8 


9x11 


126 


84 


9H X 14U 


10% X 15^ 


10x12 . 


120 


80 


lOH X 1'2U 


llli X 1318 


10 X 11 


140 


93 


ml X 14H 


llli X 151S 


10x16 


160 


107 


10HX16H 


llli X 1778 


12x15 


180 


120 


12% X 15^ 


14i^ X 17 


12x19 


228 


152 


12K X 19^ 


14iV X 21 


14x22 


308 


205 


14^3 X 2273 


I614 X 24K 


15 x 25 


375 


250 


15^8 x25J^ 


17^ X 27% 


16 X 20 


320 


213 


167/8 X 20^3 


18x^5 X 22/9 


16x24 


384 


256 


16/8 x24% 


18i«s X 26^ 


20 X 20 


400 


267 


20ii X 20it 


22^ X 223/g 


20 X 24 


480 


320 


20^tx211§ 


2-23/8 X 26>i 


20 X 26 


520 


347 


20iS x 2611 


22ys X 283/^ 


21 X 29 


609 


403 


2Ut X 29i§ 


28^8 X313^ 


27x27 


729 


486 


27i| X 2711 


29K X 29^ 


27x88 


1026 


684 


27iix38i| 


293^ X 403^ 


30x30 


900 


600 


30igx301| 


32^ X 32 ^>^ 



Dimensions of different makes of registers vary slightlj^ 
are for Tuttle & Bailey manufacture. 

*The Model Boiler Manual. 



The above 



350 



TABLE 18. 



Capacities of Warm Air Furnaces of Ordinary Construction in 
Cubic Feet of Space Heated.* 



Divided space 


Fire-pot 


Undivided space 


+10° 


0<^ 


—10° 


Diam. 


Area 


+ 10° 


0° 


—10° 


12000 


10000 


8000 


18 in. 


1.8 sq. ft. 


17000 


14000 


12000 


14000 


12000 


10000 


20 " 


2.2 " 


22000 


17000 


14000 


17(X)0 


14000 


12000 


22 " 


2.6 


26000 


22000 


17000 


22000 


18000 


14000 


24 '• 


8.1 


30000 


26000 


22000 


26000 


22000 


18000 


26 '• 


3.7 


85000 


30000 


26000 


30000 


26000 


22000 


28 " 


4.8 


40000 


35000 


30000 


85000 


30000 


26000 


30 •• 


4.9 


50000 


40000 


35000 



TABLE 19. 
Capacities of Hot-Air Pipes and Registers. 



^1 






of 
first 
will 


o 


o 


.a 

O 
a? 


Equivalent ar 
round or leac 
pipe. 


Equivalent 
square or ] 
pipe. 


Cubic feet 
space on 
floor same 
heat. 


at 

<^ o 

6^ 


1.- 

«w O 

o 

a 

o3 


6x8 


6 in. 


4x8 


400 


450 


500 


8x8 


7 " 


4x10 


450 


500 


560 


8x10 


8 " 


4x10 


500 


850 


880 


8x12 


8 " 


4x11 


800 


1000 


105O 


9x13 


9 " 


4x12 


1050 


1250 


1320 


9x14 


9 " 


4x14 


1050 


1350 


1450 


10x12 


10 " 


4x14 


1500 


1650^ 


180O 


10x14 


10 " 


6x10 


1800 


2000 


2200 


10x16 


10 *' 


6x10 


1800 


200O 


220O 


12x14 


12 " 


6x12 


2200 


230O 


250O 


12x15 


12 " 


6x12 


2250 


2300 


250O 


12x17 


12 '♦ 


6x14 


23G0 


2600 


280O 


12x19 


12 ** 


6x14 


2300' 


2600 


2800 


14x18 


14 " 


6x16 


280O 


3000 


3200 


14x20 


14 " 


6x16 


2900 


3000 


3200 


14x22 


14 " 


8x16 


3000 


320O 


3400 


16x20 


16 " 


8x18 


3600 


400O 


4250 


16x24 


16 " 


8x18 . 


3700 


4000 


4250 


20x24 


18 " 


10x20 


4800 


540O 


5750 


20x26 


20 " 


10x24 


6000 


7000 


7450 



♦Federal Furnace League Handbools. 
tKidder's Arch, and B'ld'rs. Pocket-Book. 



351 



TABLE 20. 
Air Heating Capacity of AVarni Air Furnaces.* 







Total 








cross sec. 




Fire-pot 


Casing 


area of 


Xo. and size of heat pipes that 






heat 


may be supplied 






pipes 




Diam 


Area 


Diam. 


180 sq. in. 




18 in. 


1.8 sq. ft. 


30"-32" 


3-9" or 4-8" 


20 " 


2.2 ** 


34"-36" 


280 " 


2-10" and 2-9" or 3-9" and 2-8" 


22 '* 


2.6 " 


86''-40" 


360 " 


3-10" and 2-9" or 4-9" and 2-8" 


24 " 


8.1 " 


40"-44" 


470 " 


3-10", 1-9" and 2-8" or 2-10" and 5-8* 


26 " 


3.7 " 


44^-50'' 


565 " 


5-10" and 3-9" or 3-10", 4-9" and 2-8" 


28 " 


4.3 " 


48"-56" 


650 " 


2-12", 3-10" and 8-9" or 5-10", 3-9" and 2-8" 


80 " 


4.9 " 


52"-60'' 


730 " 


3-12", 3-10" and 8-9" or 5-10", 5-9" and 1-8" 



TABLE 21. 

Sectional Area (Square Inches) of Vertical Hot Air Flues, 
Xatural Draft, Indirect Systeni.t 

Outside temperature 50° F. Tlue temperature 90° P. 







STEAM 






WATER 




Sq. ft. 


































cast iron 




re 




^ 




Ti 




JH 


radiation 




M 


§^ 


3 f-< 


tt^ 


^ 


^^ 


3 fH 




.^ o 


S 9 


^ 





ii 


^. 


s: 







^^ 


^■^ 


E^^ 


^■S 


^■^ 


a: CO 




1^^ 


to 50 


100 


75 


63 


60 


75 


63 


60 


CO 


50 '' 75 


150 


113 


94 


80 


113 


94 


80 


80 


75 " 100 


200 


150 


125 


100 


150 


125 


100 


100 


100 " 125 


250 


188 


156 


125 


188 


156 


125 


125 


125 " 150 


300 


225 


188 


150 


225 


188 


150 


150 


150 '* 175 


850 


263 


219 


175 


263 


219 


175 


175 


175 ** 200 


400 


300 


250 


200 


300 


250 


200 


200 


200 " 225 


450 


338 


281 


225 


338 


281 


225 


225 


225 " 250 


500 


375 


313 


250 


375 


313 


250 


250 


250 " 275 


550 


413 


844 


275 


413 


344 


275 


275 


275 '' 300 


600 


450 


375 


800 


450 


875 


300 


300 


300 •' 325 


650 


488 


406 


325 


488 


406 


325 


325 


325 " 850 


700 


525 


438 


350 


525 


438 


350 


850 


850 " 875 


750 


563 


469 


375 


563 


469 


375 


375 


375 ** 400 


800 


600 


500 


400 


600 


500 


400 


400 


Velocity- 


















feet per sec. 


21/2 


41/2 


51/2 


61/2 


11/2 


21/2 


4 


4 


Effective area 


















of register. 


1.00 


1.50 


1.83 


2.17 


1.00 


1.00 


1.33 


1.33 


Factor for 



















^Federal Furnace League Handbook, 
rriie Model Boiler Manual. 



352 



TABLE 22. 
Sheet Metal Dimensions and Weights, 





Approximate 


Wt. per sq 


. ft. in lbs. 




Decimal 


Iron 


Steel 


U. S. gage 


gage 


millimeters 


480 lbs. per 
cu. ft. 


489.6 lbs. per 
cu. ft. 


numbers 


' 0.002 


0.05 


0.08 


0.082 




0.004 


0.10 


0.16 


0.163 




0.006 


0.15 


0.24 


0.245 


38-39 


0.008 


0.20 


0.32 


0.326 


34-35 


0.010 


0.25 


0.40 


0.408 


32 


0.012 


0.30 


0.48 


0.490 


80-31 


O.OU 


0.36 


0.56 


0.571 


29 


0.016 


0.41 


0.64 


0.653 


27-28 


0.018' 


0.46 


0.72 


0.734 


26-27 


0.020 


0.51 


0.80 


0.816 


25-26 


0.022 


0.56 


0.88 


0.898 


25 


0.025 


0.64 


1.00 


1.020 


24 


0.028 


0.71 


1.12 


1.142 


23 


0.032 


0.81 


1.28 


1.306 


21-22 


0.036 


0.91 


1.44 


1.469 


20-21 


0.040 


1.02 


1.60 


1.632 


19-20 


0.045 


1.14 


1.80 


1.836 


18-19 


0.050 


1.27 


' 2.00 


2.040 


18 


0.055 


1.40 


2.20 


2.244 


17 


0.060 


1.52 


2.40 


2.448 


16-17 


0.065 


1.65 


2.60 


2.652 


15-16 


0.070 


1.78 


2.80 


2.856 


15 


0.075 


1.90 


3.00 


3.060 


14-15 


0.080 


2.03 


3.20 


3.264 


13-14 


0.085 


2.16 


3.40 


3.468 


13-14 


0.090 


2.28 


3.60 


3.672 


13-14 


0.095 


2.41 


3.80 


3.876 


12-13 


0.100 


2.54 


4.00 


4.080 


12-13 • 


0.110 


2.79 


4.40 


4.488 


12 


0.125 


8.18 


5.00 


5.100 


11 


0.135 


3.43 


5.40 


5.508 


10-11 


0.150 


3.81 


6.00 


6.120 


9-10 


0.1G5 


4.19 


6.60 


6.732 


8-9 


0.180 


4.57 


7.20 


7.344 


7-8 


0.200 


5.08 


8.00 


8.160 


6-7 


0.220 


5.59 


8.80 


8.976 


4-5 


0.240 


6.10 


9.60 


9.792 


8-4 


0.250 


6. '35 


10.00 


10.200 


8 



For weights of galvanized iron, multiply weight, black, by:— 
No. 28 No. 20 No. 24 No. 22 No. 20 No. 18 No. 16 



1.25 



1.21 



I.IG 



1.13 



1.11 



1.08 



1.07 



353 



TABLE 23. 



Weight of Roimd Galvanized Iron Pipe and Glbows of the 
Proper Gages for Heating and Ventilating Work, 



Gage and 
weight per 
sq. ft. 


o 


Circumf. 
of pipe 
in inches 


Area in 
sq. in. 


Weight per 

running 

foot 


Weight of 
full elbow 


Gage and 
weight per 
sq. ft. 


o 


Circumf. 
of pipe 
in inches 


Area in 
sq. in. 


Weight per 

running 

foot 


^5 




3 


9.43 


7.1 


0.7 


0.4 




36 


113.10 


1017.9 


17.2 


124.4 




4 


12.57 


12.6 


1.1 


0.9 




37 


116.24 


1075.2 


17.8 


131.4 


No. 28 


5 


15.71 


19.6 


1.2 


1.2 




38 


119.38 


1134.1 


18.2 


139.4 


0.78 


6 


18.85 


28.3 


1.4 


1.7 




39 


122.52 


1194.6 


18.7 


146.0 




7 


21.99 


38.5 


1.7 


2.3 




40 


125.66 


1256.6 


19.1 


152.9 




8 


25.13 


50.3 


1.9 


2.9 


No. 20 


41 


128.81 


1320.6 


19.6 


160.7 














1.66 


42 


131 95 


1385 4 


20.1 


168.6 
176.7 
185.0 
193.4 
202.2 


No. 26 
0.91 


9 

10 
11 
12 


28.27 
31.42 
34.56 
37.70 


63.6 

78.5 

95.0 

113.1 


2.4 

2.7 
2.9 
3.2 


4.3 
5.3 
6.4 
7.6 




43 
44 
45 
46 


135!09 
138.23 
141.37 
144.51 


1452 '.2 
1520.5 
1590.4 
1661.9 


20 '.6 
21.0 
21.5 
22.0 




13 
14 


40.84 
43.98 


132.7 
153.9 


3.4 

3.7 


8.9 
10.4 


















47 


147.65 


1734.9 


29.2 
















274.3 




15 


47.12 


176.7 


4.5 


13.5 




48 


150.80 


1809.6 


29.8 


286.6 




16 


50.27 


201.1 


4.7 


15.1 




49 


153.94 


1885.7 


30.4 


298.8 


No. 25 


17 


53.41 


227.0 


5.0 


17.0 




50 


157.08 


1963.5 


31.0 


309.9 


1.03 


18 


56.55 


254.5 


5.3 


19.1 




51 


160.22 2042.8 


31.6 


322.5 




19 


59.69 


283.5 


5.6 


21.4 


No. 18 


52 


163.36 2123.7 


32.2 


335.1 




20 


62.83 


314.2 


6.0 


23.9 


2.16 


53 

54 
55 


166.50 2206.2 
169.65 2290.2 

172.79 2375.8 


33.0 
23.6 
34.4 


349.7 
463.4 














377.2 




21 


65.97 


346.4 


7.0 


29.6 




56 


175.93 2463.0 


34.9 


390.7 




22 


69.12 


380.1 


7.3 


32.3 




57 


179.07 2551.8 


35.6 


405.1 


No. 24 


23 


72.26 


415.5 


7.7 


35.6 




58 


182.212642.1 


36.1 


418.8 


1.16 


24 


75.40 


452.4 


8.0 


38.6 




59 


185. 3512734.0 


36.7 


433.1 




25 


78.54 


490.9 


8.3 


41.7 




60 


188. 50! 2827. 4 


37.4 


448.6 




26 


81.68 


530.9 


8.7 


45.1 
















27 


84.82 


572.6 


10.9 


59.1 
















28 


87.97 


615.7 


11.4 


64.2 ! 




61 


191.64 


2922.5 


46.7 


569.7 




29 


91.11 


660.5 


11.8 


68.6 1 




62 


194.78 


3019.1 


47.5 


589.0 


No. 22 


30 


94.25 


706.9 


12.2 


73.4 ! 




63 


197.92 


3117.3 


48.3 


60S. 6 


1.41 


31 


97.39 


754.8 


li'.e 


78.3 


No. 16 


64 


201.06 


3217.0 


49.1 


628.5 




82 


100.53 


804.3 


13.0 


83.4 i 


I 2.66 


66 


207.34 


3421.2 


50.5 


666.6 




33 


103.67 


855.3 


13.5 


88.9 : 




68 


213.63 


3631.7 


52.1 


708.6 




34 


106.84 


907.9 


13.9 


94.3 




70 


219.91 


3848.5 


53.6 


750.4 




35 


109.96 


962.1 


14.3 


99.9 ' 




72 


226.19 


4071.5 


55.1 


793.4 



35i 



TABLE 24. 



Specific Heats, Coeflicients of Expansion, Coeflicients of Trans- 
mission, and Fusing'-Points of Solids, Liquids or Gases.* 



SUBSTANCE 




O 

OS 


o a 



ft 


AntiTnony 


0.0508 
0.0951 
0.0324 
0.1138 
0.1937 
0.1298 
0.0314 
0.0324 
0.0570 
0.0562 
0.1165 
0.1175 

0^0956 
0.0939 
0.5040 
0.2026 
0.2410 
0.1970 
0.1887 
1.0000 
0.0333 
0.7000 


.00000602 
.00000955 
.00001060 
.00000895 
.00000478 
.00000618 
.00001580 
.00000530 
.00001060 
.00001500 
.00000600 
.00000689 
.00000003 
.00001633 
.00001043 
.00000375 
.00006413 
.00007860 
.00002313 
.00012530 
.00008806 
.00003333 
.00015151 


.00022' 
.00404 

r00089" 
.0000008 
.000659 
.00045 

"00610" 
.00084 
.00062 
.00034 

"00170" 

.00142 

.000024 

'000002' 
.00203 

"ooooos' 

.00011 
.000002 


815 


Copper __ __ 


1949 


Gold _. 


1947 


Wrought iron 

Glass 


2975 

1832 


Cast iron 


2192 


Lead _ 


621 


Platinum 


3152 


Silver _ 


1751 


Tin _ 


446 


Steel (soft) __ - - 


2507 


Steel (hard) 

Nickel steel 36% 

Zinc 


2507 

'787 


Brass 


1859 


Ice _ __ _ - - 


32 


Sulphur _ _ 




Charcoal __ _ 




Aluminum _ 


1213 


Phosphorus 

Water 




Mercury 




Alcohol (absolute ) — 






Con- 
stant 
pres- 
sure 



Con- 
stant 
volume 



Coefficient 
of cubical ex- 
pansion at 1 
atmos. 



Air 

Oxygen 

Hydrogen 

Nitrogen 

Superheated steam 
Carbonic acid 



0.23751 

0.21751 

3.40900 

0.24380 

0.4805 

0.2170 



0.16847 

0.15507 

2.41226 

0.17273 

0.346 

0.1535 



.003671 
.003674 
.003669 
.003668 
.003726 



.0000015 
.0000012 
.0000012 
.0000012 

"00000122 



^Kent and Suplee. 



TABLE 25. 

Pressure, in Ounces, per Square Inch, Corresponding to 
A^arious Heads of Water, in Inches.* 





Decimal parts of an inch 


Head 






















in 


.0- 


.1 


.2 


.3 


.4 


.5 


.6 


.7 


.8 


.9 


inches 



























.06 


.12 


.17 


.23 


.29 


.35 


.40 


.45 


.52 


1 


.58 


.63 


.69 


.75 


.81 


.87 


.93 


.98 


1.04 


1.09 


2 


1.16 


1.21 


1.27 


1.33 


1.39 


1.44 


1.50 


1.56 


1.62 


1.67 


■ S 


1.73 


1.79 


1.85 


1.91 


1.96 


2.02 


2.08 


2.14 


2.19 


2.25 


4 


2.81 


2.37 


2.42 


2.48 


2.54 


2.60 


2.66 


2.72 


2.77 


2.83 


5 


2.89 


2.94 


3.00 


3.06 


3.12 


3.18 


3.24 


3.29 


3.35 


3.41 


6 


3.47 


3.52 


3.58 


3.64 


3.70 


3.75 


3.81 


3.87 


3.92 


3.98 


7 


4.04 


4.10 


4.16 


4.22 


4.28 


4.33 


4.39 


4.45 


4.50 


4.56 


8 


4.62 


4.67 


4.73 


4.79 


4.85 


4.91 


4.97 


5.03 


5.08 


5.14 


9 


5.20 


5.26 


5.31 


5.37 


5.42 


5.48 


5.54 


5.60 


5.66 


5.72 



TABLE 26. 

Height of Water Column, in Inches, Corresponding to Pres- 
sures, in Ounces, per Square Inch,* 









Decima 


1 parts of an ounce 




Pressure 






















in ounces 






















per square 


.0 


.1 


.2 


.3 


.4 


.5 


.6 


.7 


.8 


.9 


inch 



























.17 


.35 


.52 


.69 


.87 


1.04 


1.21 


1.38 


1.56 


1 


1.73 


1.90 


2.08 


2.25 


2.42 


2.60 


2.77 


2.94 


3.11 


3.29 


2 


3.46 


3.63 


3.81 


3.98 


4.15 


4.33 


4.50 


4.67 


4.84 


5.01 


3 


5.19 


5.36 


5.54 


5.71 


5.88 


6.06 


6.23 


6.40 


6.57 


6.75 


4 


6.92 


7.09 


7.27 


7.44 


7.61 


7.79 


7.96 


8.13 


8.30 


8.48 


5 


8.65 


8.82 


9.00 


9.17 


9.34 


9.52 


9.69 


9.86 


10.03 


10.21 


6 


10.38 


10.55 


10.73 


10.90 


11.07 


11.26 


11.43 


11.60 


11.77 


11.95 


7 


12.11 


12.28 


12.46 


12.63 


12.80 


12.97 


13.15 


13.32 


13.49 


13.67 


8 


13.84 


14.01 


14.19 


14.36 


14.53 


14.71 


14.88 


15.05 


15.22 


15.40 


9 


15.57 


15.74 


15.92 


16.09 


16.26 


16.45 


16.62 


1C.76 


16.95 


17.14 



'Suplee's M. E. Reference Book. 



356 



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" OOi-lrHi-li-lr-l ■" 



(MC-lCvlCOCvIO-lCvlCOCOCOCOCOCOCOCOC^iCOCO 



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i^COOiG<l'M^OOr-iCOCOO-r<MO'+l 
(MCO"^COOOOCOCOO^OOOOO 



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(M 00 CO T-H Q O O Lr 
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8§ 

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THiHjH<MC<JCOCO'^-^lOCOX>r>-OOOr-i(MCO'*LOCOt- 



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r-lrHi-IC<JOJCOCO-*"«1liC)COl:^OOCiOi-IC<JCO'*OCOl> 



357 



TABLE 28. 
E^xpnnsion of AVrought-Iron Pipe on the Application of Heat.* 



Temp, air 
















^vhen 




Increase in 


length in inches 


per 100 feet 




pipe 








when heated to 








is fitted 
















Deg. F. 


IGO 


180 


200 


212 


220 


228 


240 


274 





1.28 


1.44 


1.60 


1.70 


1.76 


1.82 


1.93 


2.19 


32 


1.02- 


1.18 


1.34 


1.44 


1.50 


1.57 


1.66 


1.94 


50 


.88 


1.04 


1.20 


1.30 


1.36 


1.42 


1.53 


1.79 


70 


.73 


.88 


1.04 


1.14 


1.20 


1.26 


1.36 


1.63 



TABLE 29. 
Tapping: List of Direct Radiators.f 

STEAM. 



1 

ONE-PIPE WORK. 


TWO-PIPE WORK. 


Radiator area 
square feet 


Tapping diam- 
eter—inches 


Radiator area 
square feet 


Tapping diam- 
eter—inches 


0—24 

24— 60 

60 — 100 

100 and above 


1 

IVi 
IV2 
2 


— 48 
43 — 96 
9<3 and above 


1 X % 

IVLxl 

iy2Xli/4 



WATER. 

Tapped for supply and return. 



Radiator area 
square feet 


Tapping diameter 
inches 


— 40 

40 — 73 

73 and above. 


1 



^Holland Heating Manual. 
fAmerican Radiator Co. 



358 



TABLE 30. 
Pipe I^qiialixntion. 



(See also Table 10) 



Tills tabic shows the relattion of the 
combined area of small round warm 
air ducts or pipes to the urea of one 
large main duct. 

The bold figures at the top of the 
column represent the diameters of 
the small pipes or ducts; those in 
the left-hand vertical columns 
sure the diameters of the main 
pipes. The small figures sliow ^ 

the number of small pipes that 
each main duct will supply. 



CO ^ ^ ^' ^' p^ jj, rA ^ 

^ rH (>> CO -* lO CO r- OS O rH •^'^ 

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CO rH 0> CO '^ »0 CO CO Ci rH C^J CO '<^. 

tH rH T-H iH iH rH pH r-I C^ Ci ci '^> 



i-H W 



KxaTnpIo.— 'J'o supply sixteen 
10-inch pipes: liefer to eoliiinn 
having 10 at top; follow 
down to small figure HJ, 
thence left on the hori- 
zontal lino of the bold- 
face figure in the 
outside column, and 
we find that one 
3(>-incii main will 
supply air for 
the sixteen 
10- inch 
pipes. 



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CO ift 

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CM ^ ^ ^ 



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»- ^. T- r- »— T- ,^ V- ,_ ,— CM CM CM CM CM eg 



CO I— CO o> o .— CM CO •«• in CO r— eo 

CM <M CM CM CO CO CO CO CO CO CO CO CO 



359 



TABLE 31. 



Capacities of Hot Water Risers in Square Feet of Direct 

Radiation.* 

Drop in temperature 20°. 



D. of 

riser 

inches 


First 
floor 


Second 
floor 


Third 
floor 


Fourth 
floor 


Fifth 
floor 


Sixth - 
floor 


1 


12 
22 

88 
66 
140 
240 
850 
510 
700 


17 

82 

50 

92 

196 

328 

490 

705 

980 


21 

40 
70 
112 
238 
40O 
595 
860 
1190 


24 

48 

80' 

132 

2S0 

470 

700 

1010 

1280 







l^A 


88 
145 
310 
515 
770 
1110 
1540 




1% 




2 




21/^ 




8 

4 


850 
1215 
1660 



A small pipe should never be run to a great height where it 
only supplies one radiator. It is better to- have limits for pipes 
as follows: 



D. in inches: 

Height in feet: 



% 

20 


1 
30 


45 


1^2 

60 


2 

80 



(Reduce size by 
floors.) 



TABLE 32. 
Capacities of Pipes in Square Feet of Direct Steam Radiation.f 







i 


a ^ 






a • 


i 


o 





a 


1 


=4-1 



«4-l 



S 


a 




S ?-• ai 


.0 

1— 1 






r: ^ ^ 

S fH 


02 

1— ^ 




pg.s 


Q^B 


ci 


UO 


pg.s 


Q£i.S 


05 


U^ 


1 


1 


36 


60 


5 


31/2 


3720 


6200 


1V4 


1 


72 


120 


6 


31/2 


60OO 


10000 


1V2 


11/4 


120 


200 1 


7 


4 


9000 


150OO 


2 


iy2 


280 


480 1 


8 


4 


1280O 


21600 


21/2 


2 


528 


880 


9 


41/2 


1780O 


3O00O 


8 


21/2 


900 


1500 


10 


5 


23200 


39000 


81/2 


21/2 


1320 


2200 i 


12 


6 


37000 


620O0 


4 


3 


1920 


3200 i 


14 


7 


54000 


92C00 


4y2 


3 


2760 


4600 


16 


8 


76000 


130000 



♦International Correspondence School. 
IKent's M. E. Pocket-Book. 



360 



TABLE 33. 

Capacities of Hot Water Pipes in Square Feet of Direct 
' Radiation.* 





Indi- 


















rect 






Direct radiation. 






Diameter 


radi- 


Keight of coil above bottom of boiler, in 


ft. 


of pipes. 


ation 
















inches 





















10 


20 


30 


40 


50 


70 


100 




sq. ft. 


sq. ft. 


gq. ft. 


sq. ft. 


sq. ft. 


sq. ft. 


sq. ft. 


sq. ft. 


% 


49 


50 


52 


53 


55 


57 


61 


68 


1 


87 


89 


92 


95 


98 


101 


108 


121 


IV4 


136 


140 


144 


149 


153 


158 


169 


189 


11/2 


196 


202 


209 


214 


222 


228 


243 


271 


2 


349 


359 


370 


380 


393 


405 


433 


483 


21/2 


546 


561 


577 


595 


613 


633 


678 


755 


3 


785 


807 


835 


856 


888 


912 


974 


1086 


31/2 


1069 


1099 


1132 


1166 


1202 


1241 


1327 


1480 


4 


1395 


1436 


1478 


1520 


1571 


1621 


1733 


1933 


41/2 


1767 


1817 


1871 


1927 


1988 


2052 


2193 


2445 


5 


2185 


2244 


2309 


2376 


2454 


2531 


2713 


3019 


6 


3140 


3228 


3341 


3424 


3552 


3648 


3897 


4344 


7 


4276 


4396 


4528 


4664 


4808 


4964 


5308 


5920 


8 


5580 


5744 


5912 


6080 


6284 


6484 


6932 


7735 


9 


7068 


7268 


7484 


7708 


7952 


8208 


8774 


9780 


10 


8740 


8976 


9236 


9516 


9816 


10124 


10852 


12076 


11 


10559 


10860 


11180 


11519 


11879 


12262 


13108 


14620 


12 


12560 


12912 


13364 


13696 


14208 


14592 


15588 


17376 


13 


14748 


15169 


15615 


16090 


16591 


17126 


18307 


20420 


14 


17104 


17584 


18109 


18656 


19232 


19856 


21232 


23680 


15 


19634 


20195 


20789 


21419 


22089 


22801 


24373 


27168 


16 


22320 


22978 


23643 


24320 


25136 


25936 


27728 


30928 



TABLE 34. 

Capacities of Hot Water Mains in Square Feet of Direct 

Radiation.! 





Total estimated length of circuit 


D. of 






















mams 


100 


200 


30O 


400 


500 


60O 


700 


80O 


900 


1000 


1 


20 




















11/4 


35 


20 


















11/2 


56 


40 


25 
















2 


116 


85 


70 


50 














2y2 


220 


150 


120 


100 


90 












3 


345 


240 


200 


170 


150 


140 


125 


110 


100 


90 


3y2 


500 


340 


280 


245 


225 


205 


190 


175 


162 


150 


4 


700 


485 


390 


340 


310 


280 


260 


240 


230 


220 


4y2 


925 


640 


535 


460 


410 


375 


345 


325 


300 


295 


5 


1200 


830 


700 


600 


540 


490 


450 


420 


400 


380 


6 


1900 


1325 


1100 


950 


850 


775 


700 


650 


620 


600 


7 




2000 


1600 


1400 


1250 


1140 


1050 


975 


925 


875 


8 








1970 


1720 


1550 


1440 


1350 


1300 


1250 


9 














1900 


1800 


1700 


1620 



♦Kent's M. E. Pocket-Book. 
flnternational Correspondence School. 

361 



xn 



a 

!^ 

ri o 

%t 

P ft 

- — ■- 

. O 

ft 

o ^ 

§ ft 

o +^ 

*::;"'!' 

® (D 

U O 

P fH 
CO r^ 
M IS 

ft o 

O c3 

ft a 

O (D 

be o 

? 

o 



Sft 
8© 






■I^A 



OU3 



F-H rH (*<J CO U2 t>- 



00 lO lO lO Tt< GO CO 



lOOO-r^OS^OCOO^QO^-^Ot-^jCOCOSO 
i-li— l(N3<iCO"^'<t<'<#iOiO«Ot-QOXi050^^ 



8> 









^k 



^"3 

CO 



^ 






^ 6 
;> ft 



•U^p'BJ 

■Wts 



•dojp 
•zo 



r-( I— I 5<J (M CO '^ «0 



Tt<(MCO^CO C0Q0LOC0.-(Cit-*O 



'n,pT3j 



•dojp 
•zo 



^— i3^0iOi-iXOXO»C;OiCO 
i-HS^ICOt'OiO— tXiO^S-MiO— (030 



>— I^X O -^ CO t^ T^l X «0 CO b- 
«C3<lXXi-IOOOw?3r-(30c-OiO 

OS Tt< OS lO ■* CO cjq 3<j I— ( I— I rH 



'u.puj 



■dojp 
•zo 



^H-^OOiOiOOOtOOOCO 

C<>35XOt>»rH^1000f^JU 

r-trHS^lOt-i— llOOiC— HtiO 

I— I <-l !>l 3S 20 -^ ?0 



lO «0 "W Tti ?0 lO l>. lO 

. '^ . , '-J i^x '"^ O X t- lO TP 

Ot^lOCOG^rH-i-H 



11, pi? J 



•dojp 
•zo 



C-.O'MO'T^SS-hOOX 
I— l^-iS^-<^?OXt^^OO-* 



<© O CO >— i rH rH 



•U.PB.T 



'dojp 
•zo 



-"if ?OXOiOOS 

t-. — < O O :o -o 

r-H r— I :c "^ «3 



•U^P'B.I 



•do.ip 
•zo 



OSfc-'MO 



O X 

o-'x^ 



■u,pi?H 



'do.ip 
•zo 






02 






^2 

•i-l N^N^J ^ X? ^ 

p^^'Jl,^5^3000'*'^»O<Dt'X0SO(5<I'#O 



3(}2 



1 


O -^ O «D -^ lO CO 

I-lOCO^co--^r-lr^(^^(3<^co^lO 
l-H i-( 0^ CO "* t- 


l-H 


lO^'*<N<M'-ia'OCO^gG<30 

I— it^T}icOir::'*'J^i-H(M<MCO-*iO 
i-H rH 3^ CO "^ r^- 


1—1 


. • - •^iS'MCiXOiX 
<MXiC-^fc-t-rHi— l5<l5<JC0'^lO 

i-H f— 1 cr^ so -^ t- 


1 


l>.(M!— I£-O'3<j-HCO«'M^COO 

• • • 3<1 t- CO -— I O 5<1 3<» 

3<Ja. h-«OC:3<)i-Hi— IG^JCO-^IS^O 

-^ rH jq CS O X 


s 

r—i 




rH 


iooxorHt-xt:^go^x^ 


i 


OOOOlOO.-lXOT*2<I?C?OXt^ 

lO — OlXCi-^O 

lOSOCOlOS^I-Hr-K^JS^lCO^^t:- 
r-H3<lCO^?00 


s 




i 






(MCiXSOCOi-HOOrHOTt^^^lt-. 

OXOirHOlCCM 

-j,_(^^5CO(M<MCOlO«>XO 
(MXCrPOXCO rH 


s 


Ot-X^COfMQOS^OCOCOCOCi 

— rH G<J <0 0^ -^ rH 


CO 


«D«05<>X5^5<J(M«OCO'*CO"*S<l 
T« Tf b- 3<1 O -* -^ 


8 


(N«»X-HCO'*O^Ci(MlO<MiO 

• • • !>. c: CO rH -^ 05 -H 


12 

I— 1 


Ob.XO^rHOg.^^gXg 
lO5^C052-^'^C0^«>XO'*'^ 

C0lCt-O-l3<l rHrHrH 


8 

»— 1 


oio:ooit-iot-.^co«ot-t-x 

CO-^'OGM — xco 

TtiOOSCOQOOS rHrirHG^ 
rH rH {3<1 


O 


^HCOrHOiO^XOsC'NtClCuO 
I-H rH(M TJH 



eeqyuT 



COCO'«*TtiiO«Ot»OOOiOrH(3<»CO 





1 


QCiC0'*<NrH0000'*lO 

t-CilOOrHt-lOCCrH 

lO'tOXCirH'T^TPX'^ 

rH rH rHrH3<J 




1 


03-lCiC;0^(MlOCO 
OX>XO^COiOC5»0 




1 


Ci«OiOrHX(M5^rHia 




S 
S 






Til 

rH 


725 
868 
1072 
1200 
1393 
1602 
1828 
2337 
3023 




1 






rH 


858 
1028 
1268 
1121 
1618 
1895 
2163 
276)5 
3580 


9-1 


i 


904 
1083 
1333 
1500 
1737 
1997 
2279 
2914 
3769 


1-^ 


8 

X 


CiOiCOr-^COClXCOLC 

irt'*'rHCi-W-^_lCiOi 
rH rH rH rH 5<l 5<1 CO CO 




1025 
1228 
1513 
1702 
1970 
22()5 
2585 
3278 
4435 




1 


Xt-X^Xt'COO'^J 

rHr-lrHrHG<J<MS<JCO'!fi 




i 






s 


co->ootN«:jci^cc^:; 




i 


t-COiClOQOCiXXiC 
:ct>'-HCcOi£2^'rrcro 
lOXCOOO^^CiOlC 
-^rHj^lS^COCOCOuS^C 




i 


^-lC<J3^C0C0^Tr«-t- 




s 

rH 


t-3<ioS3^cixt-5: 

3<JCO^^ iClOOXrH 




[OUT 
UUTQ 


^iO«Dt'XCsOS<l^ 

rHrHi— IrHrHrHj^lSvlfJ'-^ 



36:^ 



CI 
ft 







u o 






o +3 






-M :3 




•» 


^ C3 







Is 




a 


'^ ^. 











§ 




f- 




cc 


-♦i- 






~: 


H 


u 


J 


U* 


d O 


<1 


h 




;& 


C3 "S 


H 


'5 


S^ 




C3 




,«, S 




s 


-M bC 




«H 


(U r5 




© 


8 




g 


• 





1-1 ^ 




^ 


J3« 

•i-i 

i 

on 
Q 



o 



to 



10 



CO 



CM 



8;nuTj\[ 



I— I 2<l CO lO lO '^ 



p-Boq JO ssoq; 


• • t-lrH(N(M 


.T9Ci %dd} oiqno 


Oi-HfH(M(MO 


p-eaq jo ssoq; 


00 00 lO ?0 O «D 
CO Oi C- !>■ ■*! S^ 
CO «D >— • • 
. . . rH!MCO 
1—1 


ainmni 


lOCO^C^t--* 


pcaq JO SS01 


*? • r-ia<J(MCO 


.i8d q.eej oiqno 


CO lO t- Oi .-1 5<l 


P'Baq jossot: 


'^oo^^Dior- 

'^ OS rH CN CO Tfi 


jad (^88j oiqno 


r-l rH (M (m CO CO 


P'eaq jo ssoi 


• iH<MC0TliiO 


oanuini 
.lad %9Qi biqno 




P'Boq JO ssot: 




eanuiin 
jad ^88j oiqno 


CN CO lO «0 t>. Oi 


c^eoj ui 
p^aq JO ssot: 


I— 1 Tfi r— ( 1— 1 ?C -^ 

rH 5^ Tji ?6 00 rH 
I— 1 


G^nuiui 
.lad %^^J oiqno 





q.89J UI 

pijaq JO SS01 



a^ooas Had: 



t-oiooo coos 

COOO^CO JMOO 

C^ Tj< X C^ t-^ 5<l 

i-l i-KM 

oooooo 

3^CO ■* iO«Ot> 



00 



CO 



CM 



0) 



S<IC0C0^»O«D 

:C 0» 5M lO CJO — I 

3<i CO lO <;d !>• 05 



CO 
Oi lO O t- --H "Vi 

— ( -^ 1— I I— I O i-H 

^(?qTj<«O00 • 



'>q X -* o «o (n 

— (rHS^ CO oo^ 
CMCO-^lO^Ot- 



C<J F-l «0 lO t- 
cot- U2X lOb- 
r-i G^ Tt< 5C OS 3<> 



b- 1— ( lO OS (TJ ?0 
to lOCO -HOX 
1— IS^CO "* iCiO 



1>-?DCOOO 



X<M ?Oi— I lOOS 
5MOS lOCMX '^ 
1-1 rH CM CO CO '^ 



OS OS t- 1— I os^ 

?0 '"t- X X 'T^ CO 
rHCOlOXGO'C 



Tfi 1— I X lO CO o 

OS-^XCOX CO 

l-lr-l<M<MCO 



Xb-lOX_ 
OSOX<M CO I— I 

I— I Tt< ?0 O "^ OS 



posxxt-t- 

b- 1— ( iQ OS 70 r- 

i-l i-l r-l C<l 2^1 



<© '^t-S^l 

— < Tt< rri 0^ «C t- 



CO ?D OS C^l 
r-l I— I 1— 1(?^ 



t-X(M^ ^ 

CO X (3<1 CO I— I X 
5<J Tt< X 3^ b- (^J 



CO( 



■«J< Tfi CO b- <M <N 
«0 "* -^COOSiO 
(?v> lO OS • • _• 



OOOOOO 
(?q CO -^ lO ;c fc- 



364 



TABLE 38. 

Comparative Sizes of Steam Mains and Returns for Gravity 
and A aeiiuni Systems. 



Size of 


Size of 


return 


Size of 


Size of return 


supply 






supply 














pipe 


Gravity 


Vacuum 


pipe 


Gravity 


Vacuum 


% 


% 


1/2 


4 


21/2 


11/2 


1 


% 


V2 


41/2 


21/2 


11/2 


1% 


1 


1/2 


5 


3 


2 


iy2 


11/4 


% 


6 


31/2 


21/2 


2 


11/2 


% 


8 


4y2 


31/2 


21/2 


2 


1 


10 


6 


4 


8 


2 


11/1 


12 


6 


41/2 


31/2 


21/2 


11/4 


14 


7 


5 



Note.— For short runs of piping where the friction is not a serious 
matter the above table will work out satisfactorily. These sizes are 
only approximate and should be used with caution. 



TABLE 39. 
E^xpansion Tanks — Dimensions and Capacities.* 



Size in inches 


Capacity gallons 


Sq. ft. of radiation 


9x20 


51/2 


150 


10x20 


8 


250 


12x20 


10 


350 


12x24 


12 


450 


12x30 


15 


550 


12x36 


18 


650 


14x30 


20 


7G0 


14x36 


24 


850 


16x30 


26 


900 


16x36 


32 


1250 


16x48 


42 


1750 


18x60 


66 


2750 


20x60 


82 


450O 


22x60 


100 


600O 


24x60 


122 


75C0 



*The Model Boiler Manual. 



36J> 



TABLE 40. 













Sizes of Flanged 


Fittings. 










All fittings and 


^ii 


^-^ 


, .^ 


tef^ 


1 


■ ^ 




J) ^ 






flanges 


^^ 


fr 


Pa , ^ 


far:- 


M 

J 




to 

a 
a 

o 


a? 




to 


1 








!rJ ^ 


P-^ 


LJ — L 


^ "^^ --7^^ 




90° 
elbow 


45° 
elbow 


Long 
turn 
elbow 


Tee 


Cross 


Lateral 


















1 













(4-1 


0^ 


0, 

To 


0. 


:b 




0-^ 


cs 

:§ 




2 
P 


2 





^ 


s 





eg 

=+H 


II 


1- 


6l 




0«n 


Is 

Q w 


4 


9 


?-^ 


8 


71/2 


% 


61/2 


4 


10 


61/2 


13 


12 


3 


6 


n 


1 


8 


9% 


% 


8 


5 


13 


8 


16 


141/2 


31/2 


8 


13Vp 


iVs 


8 


11% 


% 


9 


6 


16 


9 


18 


i7y2 


41/2 


10 


16 


1,^. 


12 


1414 


% 


11 


7 


20 


11 


22 


201/2 


5 


12 


19 


1% 


12 


17 


% 


12 


7V2 


22 


12 


24 


241/2 


514 


14 


21 


1% 


14 


183/4 


1 


14 


71/2 


24 


14 


28 


27 


6 


16 


23V, 


hh 


16 


2IV4 


1 


15 


8 


28 


15 


80 


30 


61/a 


20 


271/2 


IH 


20 


25 


Wh 


18 


91/2 


32 


18 


36 


35 


8 


24 


32 


178 


20 


291/2 


IVs 


22 


11 


36 


22 


44 


401/2 


9 



TABLE 41. 
Dimensions of Ells and Tees for Wrought Iron Pipe. 




Size 


E 


R 


D 


a 


t 


L 


T 


^A 


% 




1 3 


.'« 


A 


l-% 


H 


% 


% 


/8 


1- 


K 


1% 


1-/2 


H 


H 


Vb 


y. 


1-/8 


/8 


K 


1-K 


/s 


/4 


l-H 


%. 


l-'A 


l-?« 


K 


2-% 


1-/8 


% 


1-3/8 


i-U 


l-.% 


1-1% 


A 


2-3/i 


1-3/8 


1- 


l-.'e 


i-% 


1-/8 


1-/8 


1^5 


3-/8 


1-1^^ 


1-H 


l-K 


l-'A 


2-1/i 


2- 


(1 


3-M 


1-/8 


l-'A 


2- 


1-/b 


2-V^ 


2-14 


4- 


2- 


2- 


2-3/s 


2-/8 


s-% 


2-/8 


K 


4-K 


2-% 


2-M 


2-% 


2-^ 


4- 


3-^ 


M 


5 M 


2-/8 


3- 


s-H 


2-3/ 


4-^8 


4- 


% 


6-M 


3-^ 


3-^ 


S-Vs 


3-/8 


5-K 


4-/8 


/a 


7-34 


8-/8 


4^ 


4- 


3-3/8 


5-/8 


5-M 


1- 


8- 


4- 


4-/2 


4-3/8 


4- 


Q-Va 


6- 


1- 


8-% 


4-% 


6- 


4-/8 


4-/8 


Q-'A 


6-"^^ 


1-/8 


9-/s 


4-K 


6- 


5-^ 


4-/8 


8-y2 


7-/8 


1-/8 


11- 


5-^ 



366 



TABLE 42. 

Loss of Pressure in Pipes 100 Feet Lon^ in Ounces per 
Square Inch when Delivering Air at the Velocities Given. 



city 

t. 
min. 


Diameter of pipe in inches 


Velo 
in f 
per 


1 


2 


3 


4 


6 


8 


10 


12 


14 


16 


18 


800 


0.100 


O.OoO' 0.033 


0.025 


0.017 


0.012 


0.010 


0.008 


0.007 


0.006 


0.006 


400 


0.178 


0.088 0.059 


0.044 


0.030 


0.022 


0.018 


0.015 


0.013 


0.011 


0.010 


600 


0.400 


0.200 0.133 


0.100 


0.067 


0.050 


0.040 


0.033 


0.029 


0.025 


0.022 


800 


0.711 


0. 3561' 0.237 


0.178 


0.119 


0.089 


0.071 


0.059 


0.051 


0.044 


0.040 


1000 


1.111 


0.556; 0.370 


0.278 


0.185 


0.139 


0.111 


0.092 


0.079 


0.069 


0.062 


1200 


1.600 


0.800 0.533 


0.400 


0.267 


0.200 


0.160 


0.133 


0.114 


0.100 


0.089 


1500 


2.500 


1.250, 0.833 


0.625 


0.417 


0.312 


0.250 


0.208 


0.179 


0.1561 0.139 


1800 


3.600 


1.800 1.200 


0.900 


0.600 


0.450 


0.360 


0.300 


0.257 


0.225 


0.200 


2400 


6.400 


3.200 2.133 


1.600 


1.067 


0.800 


0.640 


0.533 


0.457 


0.400 


0.356 




20 


24 


28 


32 


86 


40 


44 


48 


52 


56 


60 


800 


0.005 


0.004 0.0O4 


0.003 


0.033 


0.002 


0.002 


0.002 


0.002 


0.002 


0.002 


400 


0.009 


0.007 


0.006 


0.006 


0.005 


0.004 


0.004 


0.004 


0.003 


0.003 


0.003 


600 


0.020 


0.017 


0.014 


0.012 


0.011 


0.010 


0.009 


0.008 


0.008 


0.007 


0.007 


800 


0.036 


0.029| 0.025 


0.022 


0.020 


0.018 


0.016 


0.015 


0.014 


0.013 


0.012 


1000 


0.056 


0.046! 0.040 


0.035 


0.031 


0.028 


0.025 


0.023 


0.021 


0.020 


0.019 


1200 


0.080 


0.067i 0.057 


0.050 


0.044 


0.040 


0.036 


0.033 


0.031 


0.029 


0.027 


1500 


0.125 


0.104i 0.089 


0.078 


0.069 


0.062 


0.057 


0.052 


0.048 


0.045 


0.042 


1800 


0.180 


0.167i 0.129 


0.112 


0.100 


0.090 


0.082 


0.075 


0.069 


0.064 


0.060 


2400 


0.320 


0.313' 0.239 


0.200 


0.178 


0.160 


0.145 


0.133 


0.123 


0.119] 


0.107 



Diagrams for Pipe Sizes and Friction Heads. 

To illustrate the use of the two following diagrams, ap- 
ply to the pipe line, B, C, Art. 147. First, let I = 1500 feet, 
cZ = 8 inches and v = 5 feet per second. Trace along" the 
velocity line until it intersects the diameter line, then fol- 
low the ordinate to the top of the page and find the friction 
head, 13 feet for 1000 foot run or 19.5 feet for the 1500 foot 
run. Second, let Q = 1.75 cubic feet per second and (Z = 8 
inches. Trace to the left along" the horizontal line represent- 
irg- the volume of 1.75 cubic feet until it intersects the 
diameter line, then read up and find the same friction head 
as before. Third, let the allowable friction head for 1500 
feet of main be 19 feet, when Q = 1.75 cubic feet per second 
or when v = 5 feet per second. Reverse the process g"iven 
above and find an 8 inch pipe. 



367 



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368 



«ft iO<MO <D ^o*" ^ tnrsirg £ 0^95 o qo o o o O oo o q p o oo o oo 
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369 



TABLE 43, 
Temperatures for Testing Direct Steam Radiation Plants.* 





Test 
condi- 


Steam 
Tem- 
pera- 


Steam pressure intended for 


zero 


weather 




« 






















03 
> 


tion 


ture 


lb. 


1 lb. 


2 lb. 


3 lb. 


4 lb. 


5 lb. 


6 lb. 


7 lb. 


8 lb. 


9 lb. 


10 1b. 


•m 

o 


10 in. 


192.0 


63.3 


62.3 




















m 


9 " 


194.5 


64.2 


63.2 


62.3 


















Si 


8 *' 


197.0 


65.0 


64.0 


63.0 


62.2 


















7 ** 


199.0 


65.6 


64.7 


63.7 


62.8 


62.0 














l-l 


6 " 


201.0 


66.3 


65.3 


64.3 


63.4 


62.6 


62.0 












. 


5 ** 


203.0 


67.0 


66.0 


65.0 


64.0 


63.3 


62.6 


61.9 










.d 


4 ** 


205.0 


67.6 


66.6 


65.6 


64.7 


63.9 


63.2 


62.5 


61.7 








. 


3 " 


207.0 


68.3 


67.2 


66.2 


65.3 


64.5 


63.8 


63.1 


62.3 


61.7 






00 


2 " 


208.5 


68.8 


67.7 


66.7 


65.7 


65.0 


64.2 


63.6 


62.8 


62.0 


61.5 






1 " 


210.5 


69.4 


68.3 


67.5 


66.4 


65.6 


64.8 


64.2 


63.3 


62.6 


62.1 


61.5 


1 


lb. 


212.0 


70.0 


68.8 


67.8 


66.9 


66.1 


65.3 


64.6 


63.8 


63.1 


62.6 


62.0 


P< 


1 " 


215.5 


71.2 


70.0 


69.0 


68.0 


67.2 


66.3 


65.8 


65.0 


64.2 


63.7 


63.0 


55 


2 ** 


218.7 


72.1 


71.0 


70.0 


69.2 


68.2! 67.3 


66.7 


65.9 


65.1 


64.5 


64.0 


^ 


3 " 


221.7 




72.0 


71.0 


70.0 


69.2 


68.3 


67.6 


66.7 


66.0 


65.4 


64.8 


03 


4 ♦* 


224.5 






71.8 


70.8 


70.0 


69.2 


68.4 


67.5 


66.7 


66.2 


65.7 


en 


5 " 


227.2 








71.7 


70.8 


70.0 


69.2 


68.3 


67.6 


67.0 


66.3 


6 " 


229.8 










71.7 


70.8 


70.0 


69.2 


68.4 


67.7 


67.2 




7 ** 


232.4 












71.7 


70.8 


70.0 


69.2 


68.6 


68.0 


t-i 
P. 


8 " 


234.9 














71.7 


70.8 


70.0 


69.3 


68.7 


O) 


9 " 


237.3 
















71.5 


70.5 


70.0 


69.3 


be 


10 " 


239.4 


















71.3 


70.7 


70.0 


Factors 


.670 


.675 


.678 


.684 


.688 


.692 


.694 


.698 


.702 


.705 


.707 



The temperatures in this table are for a plant designed for 0° and 70". 

Example.— It is desired to test a plant designed for 5 pounds gage 
pressure on a day when the outside temperature is 22 degrees. What 
should be the temperature in the rooms with steam at 3 pounds gage 
pressure? It will be noted in the vertical column marked 5 pounds, that 
opposite the 3 pound pressure 68.3 degrees may be expected on a zero 
day. As the temperature was 22 degrees above we must add 22 times 
.692, or 15.2 degrees, thus making a total of 83.5 degrees, the tempera- 
ture which should exist indoors. 

*W. W. Macon. 



370 



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CO 



(M (M 






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CO I i-< 00 

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CO 



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ft ft ^ «0 
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371 



TABLE 45. 

Percentage of Heat Transmitted by Varions Pipe-Coverings, 

From Tests Made at Sibley College, Cornell University, 

and at 3Iichigan University.* 

Relative amount 
Kind of covering of heat 

transmitted 

Naked pipe 100. 

Two layers asbestos paper, 1 in. hair felt, and canvas 

cover 15.2 

Two layers asbestos paper, 1 in. hair felt, canvas 

cover wrapped with manilla paper 15. 

Two layers asbestos paper, 1 in. hair felt 17. 

Hair felt sectional covering", asbestos lined 18.6 

One thickness asbestos board 59.4 

Four thicknesses asbestos paper 50.3 

Two layers asbestos paper 77.7 

Wool felt, asbestos lined 23.1 

Wool felt with air spaces, asbestos lined 19.7 

Wool felt, plaster paris lined 25.9 

Asibestos molded, mixed with plaster paris 31.8 

Asbestos felted, pure long fibre 20.1 

Asbestos and sponge 18.8 

Asbestos and wool felt 20.8 

Magnesia, molded, applied in plastic conditnon 22.4 

Magnesia, sectional 18.8 

Mineral wool, sectional 19.3 

Rock wool, fibrous 20.3 

Rock wool, felted 20.9 

Fossil meal, molded, % inch thick 29.7 

Pipe painted with black asphaltum 105.5 

Pipe painted with light drab lead paint 108.7 

Glossj^ white paint 95.0 

^Carpenter's H. and V. B. 

Note. — These tests agree remarkably well with a series 
made by Prof. M. E. Cooley of Michigan University, and also 
with some made by G. M. Brill, Syracuse, N. Y., and reported 
in Transactions of the American Society of Mechanical En- 
gineers, vol. XVI. 



372 



TABLE 46. 
Factors of Evaporation. 



Gage 


1 


10 


20 


30 


50 


100 


1-^5 


135 


150 


175 


pressure 














1 






Peed 
water 


Pactors of evaporation 


212 


1.0003 


1.0103 


1.0169 


1.0218 


1.0290 1.0396 


1.0431 


1.0443 


1.0460 


1.0483 


200 


1.0127 


1.0227 


1.0293 


1.0343 


1.0414 


1.0520 


1.0555 


1.0567 


1.0584 


1.0608 


185 


1.0282 


1.0382 


1.0448 


1.0498 


1.0569 


1.0675 


1.0710 


1.0722 


1.0739 


1.0763 


170 


1.0437 


1.0537 


1.0603 


1.0653 


1.0724 


1.0830 


1.0865 


1.0877 


1.0894 


1.0917 


155 


1.0592 


1.0692 


1.0758 


1.0807 


1.0878 


1.0985 


1.1020 


1.1032 


1.1048 


1.1072 


140 


1.0715 


1.0846 


1.0912 


1.0962 


1.1033 


1.1139 


1.1174 


1 1186 


1.1203 


1.1227 


125 


1.0901 


1.1001 


1.1067 


1.1116 


1.1187 


1.1293 


1.132S 


1 1341 


1 1357 


1.1381 


110 


1.1055 


1.1155 


1.1221 


1.1270 


1.1341 


1.1447 


1.1482 


i 1495 


1 1511 


1.1535 


95 


1.1209 


1.1309 


1.1375 


1.1424 


1.1495 


1.1602 


1.1637 


1.1649 


1 1665 


1.1689 


80 


1.1363 


1.1463 


1.1529 


1.1578 


1.1650 


1.1756 


1.1791 


1.1803 


1.1820 


1.1843 


65 


1.1517 


1.1617 


1.1683 


1.1733 


1.1804 


1.1910 


1.1945 


1.1957 


1.1974 


1.1997 


50 


1.1672 


1.1772 


1.1838 


1.1887 


1.1958 1.2064 


1.2099 


1.2112 


1.2128 


1.2152 


35 


1.1827 


1.1927 


1.1993 1.2042 1.2113 1.2219 


1.2255 


1.2267 


1.2283 


1.2307 



TABLE 47. 

Per Cent, of Total Heat of Steam Saved per Decree Increase 

of Feed AVater. 



Initial 




Gage pressure 


in boiler, lbs. per 


sq. in. 




temp. 
of feed 

























20 


40 


60 


80 


100 


120 


140 


160 


180 


32 


.0872 


.0861 


.0855 


.0851 


.0847 


.0844 


.0841 


.0839 


.0837 


.0835 


40 


.0878 


.0867 


.0861 


.0856 


.0853 


.0850 


.0847 


.0845 


.0843 


.0839 


50 


.0886 


.0875 


.0868 


.0864 


.0860 


.0857 


.0854 


.0852 


.0850 


.0846 


60 


.0894 


.0883 


.0876 


.0872 


.0867 


.0864 


.0862 


.0859 


.0856 


.0853 


70 


.0902 


.0890 


.0884 


.0879 


.0875 


.0872 


.0869 


.0867 


.0864 


.0860 


80 


.0910 


.0898 


.0891 


.0887 


.0883 


.0879 


.0877 


.0874 


.0872 


.0868 


100 


.0927 


.0915 


.0908 


.0903 


.0899 


.0895 


.0892 


.0890 


.0887 


.0883 


120 


.0945 


.0932 


.0925 


.0919 


.0915 


.0911 


.0938 


.0906 


.0903 


.0899 


140 


.0963 


.0950 


.0943 


.0937 


.0932 


.0929 


.0925 


.0923 


.0920 


.0916 


160 


.0982 


.0968 


.0961 


.0955 


.0950 


.0946 


.0943 


.0940 


.0937 


.0933 


180 


.1002 


.0988 


.0981 


.0973 


.0969 


.0965 


.0961 


.0958 


.0955 


.0951 


200 


.1022 


.1008 


.0999 


.0993 


.0988 


.0984 


.0980 


.0977 


.0974 


.0969 


220 




.1029 


.1019 


.1013 


.1008 


.1004 


.1000 


.0997 


.0994 


.0989 


240 





.1050 


.1041 


.1034 


.1029 


.1024 


.1020 


.1017 


.1014 


.1009 



Example.— Boiler pressure 120 lbs. gage, initial temperature of feed 
water 60 deg., heated to 210 deg. Then increase in temperature 150, 
times tabular figure, .0862, equals 12.93 per cent, saving. 



373 



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r-lTHi-ti-lT-lT-lrHT-I^C<iG^(M(M(M(M 


COOOrJH'^l0100i;DX.-^1^00000iC500i-ir-( 

rH r— I I— 1 r-H 


^COC<I(Mr-lOC50000r-;Cir:)»0-^COCNlr-TH 


COX>G0050T-(r-l(MCO^L'-OI:-OOC50-^C<l 
r-,T-li-lT-lrHT-ir-iT-li-li-lr-l(M<M(M 


oooooooooooooooooo 


<N 06 -^ O CO Ol 00 '^ 0' 'm' 06 "* CO (M* 00 '^ 
i-IOl-^COl-CiOC^l'^Ol^OOOCNieotOCOCO 
rHrHr-li-Hi-lrHOqCMCvJCMC^IC^ICOCOCOCO COCO 




ooDr^io^corHc;ooco»ococ<]Ocit^cO'* 



l^-^T— lOOLOCMCiCOCOOI^'^CiCDCOOt^-^ 
COrHCiCO-<*i(MCii:^incOOOO»OCOr-(CiCO'* 

10 <© o* t^ 00 05 05 o r-H c<i CO co' ■^' 10 1:0' co' I^ 00* 

l—ii— li— IrHi— ItHi— li-Hi— (1— ii—t 

CO o o 10 ^tH "* CO CO (M* (m' I— ' T— I o O 0' ci 00' 00 

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r^^-^r^r-i1-^]-,I-l1-lT-^^Hr^(^^G^I(^a 



"^T^lOlJtlCOCOr^r^OOOOCiCiCiOrHi— ((M'M 
OOC<ICOO'*00(MCOO^OO(Ml^i— '»-OOiC0r^ 
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ooiooooiO'O 000 0000000 

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THr-lr-li-li-lTH!-<<M(M<N2<I(MtM(MC<lC0CO 



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.74 



TABLE 49. 

Steam Consumption of Various Types of Non-Condensing 
Engines.* (Approximate). 

Pounds per indicated horse-power hour. 



Kg 


Simple throt- 
tling 100 lbs. 
at throttle 


Simple auto- 
matic 100 lbs. 
initial 


Simple Corliss 
100 lbs. 
initial 


Simple four 
valve 100 
lbs. initial 


Compound 
four valve 
and Corliss 
100 lbs. 
initial 


Compound 
four valve 
and Corliss 
125 lbs. 
initial 


Compound 
four valve 
and Corliss 
150 lbs. 
initial 


10 


52 














20 


50 


40.0 












30 


49 


39.0 












40 


48 


38.0 












50 


48 


38.0 


34.5 


35.0 








60 


47 


36.0 


32.5 


33.0 








70 


47 


35.0 


31.5 


32.0 








80 


46 


34.0 


30.5 


31.0 








90 


45 


33.0 


29.5 


30.0 








100 


45 


32.0 


28.5 


29.0 








150 


44 


31.5 


28.0 


28.5 


22.5-23 


21.5-22 


21-21.5 


200 


43 


30.5 


27.0 


27.5 


22-22.5 


21-21.5 


20.5-21 


250 


43 


30.0 


26.5 


27.0 


22-22.5 


21-21.5 


20-20.5 


300 


42 


29.0 


25.5 


26.0 


22-22.5 


20.5-21 


20-20.5 


400 


41 


28.5 


25.0 


25.5 


21.5-22 


20-20.5 


19.5-20 


500 


41 


28.5 


25.0 


25.5 


20-21.5 


19.5-20 


19-19.5 



The foregoing table was compiled principally from the records of a 
large number of actual tests of engines of various makes, under reason- 
ably favorable conditions. It is based upon the actual weight of con- 
densed exhaust steam. 

*Atlas Engine Works Catalog. 



875 



TABLE 50. 

Speeds, Capaeities and Horse-Powers of "Green" Steel Plate 

Fans at Varying Pressures.* 



E^l 


.26 in. 


.87 in. 


1.3 in. 


1.7 in. 


2.2 in. 


2.6 in. 


3.02 in. 


3.46 in. 


4.33 in. 


.S ^ i Pressures 




















1,4 oz. 


V2 OZ. 


% oz. 


1 oz. 


114 oz 


11/2 oz 


1% oz. 


2 oz. 


21/2 oz. 




CU. FT. 


2249 


8176 


3891 


4498 


5029 


5513 


5956 


6372 


7135 


SO 


R. P. M. 


830 


466 


571 


660 


738 


809 


874 


985 


1047 




H. P. 


.286 


.811 


1.491 


2.298 


3.218 


4.227 


5.811 


6.515 


9.120 




CU. FT. 


3289 


4581 


5605 


6477 


7242 


7937 


8584 


9173 


10268 


36 


R. P. M. 


275 


389 


476 


550 


615 


674 


729 


779 


872 




H. P. 


.418 


1.170 


2.148 


3.311 


4.625 


6.086 


7.681 


9.375 


13.125 




CU. FT. 


4398 


6214 


7617 


8815 


9864 


10799 


11679 


12483 


13981 


42 


R. P. M. 


235 


332 


407 


471 


527 


577 


624 


667 


747 




H. P. 


.557 


1.576 


2.898 


5.473 


6.300 


8.287 


10.450 


12.750 


17.825 




CU. FT. 


5750 


8128 


9937 


1150O 


12867 


14123 


15240 


16301 


18282 


48 


R. P. M. 


206 


291 


356 


412 


461 


506 


546 


584 


655 




H. P. 


.733 


2.076 


3.810 


5.880 


8.223 


10.832 


13.636 


16.670 


23.370 




CU. FT. 


7602 


10758 


13167 


15203 


I7a30 


18650 


20145 


21558 


24174 


54 


R. P. M. 


]83 


259 


317 


366 


410 


449 


485 


519 


582 




H. P. 


.970 


2.750 


5.047 


7.767 


10.880 


14.300 


18.0 7 


21.992 


30.896 




CU. FT. 


9715 


13718 


16780 


19429 


21725 


23786 


25728 


27495 


30792 


60 


R. P. M. 


165 


233 


285 


380 


869 


404 


487 


467 


523 




H. P. 


1.241 


3.506 


6.433 


9.982 


13.882 


18.230 


22.996 


28.077 


39.355 




CU. FT. 


12078 


17071 


20855 


24156 


26975 


29551 


32047 


34221 


38247 


66 


R. P. M. 


150 


212 


259 


300 


335 


367 


398 


425 


475 




H. P. 


1.542 


4.361 


7.996 


12.352 


17.238 


22.666 


28.675 


35.123 


48.895 




CU. FT. 


15608 


21942 


26918 


31108 


34835 


38115 


41169 


44109 


49312 


72 


R. P. M. 


138 


194 


238 


275 


308 


337 


364 


390 


436 




H. P. 


1.983 


5.601 


10.322 


15.881 


22.252 


29.223 


36.808 


45.013 


62.783 




CU. FT. 


20192 


28405 


34907 


40383 


45174 


49452 


53387 


57152 


63996 


84 


R. P. M. 


118 


166 


204 


236 


264 


289 


^ 312 


884 


374 




H. P. 


2.581 


7.262 


13.387 


20.650 


28.875 


87.931 


47.775 


58.450 


81.812 




CU. FT. 


23008 


32614 


39762 


46016 


51601 


56515 


60983 


6522- 


73045 


96 


R. P. M. 


103 


146 


178 


206 


231 


253 


273 


292 


327 


k 


H. P. 


2.941 


8.337 


15.261 


23.531 


32.982 


43.348 


54.511 


66.707 


93.380 




CU. FT. 


29260 


41027 


50568 


58519 


65198 


71559 


77284 


82690 


92549 


108 


R. P. M. 


92 


129 


159 


184 


205 


225 


243 


260 


291 




H. P. 


3.737 


10.4S8 


19.397 


30.060 


41.666 


54.871 


69.168 


84.556 


118.291 




CU. FT. 


36209 


51042 


62384 


71982 


80270 


88559 


95589 


102083 


114298 


120 


R. P. M. 


83 


117 


143 


165 


184 


203 


219 


284 


262 




H. P. 


4.628 


13.050 


23.925 


36.807 


51.307 


67.928 


85.495 


104.401 


146.116 




CU. FT. 


43560 


61565 


75504 


87120 


97575 


106868 


115580 


123711 


138231 


132 


R, P. M. 


75 


106 


130 


150 


168 


184 


199 


213 


288 




H. P. 


5.568 


15.730 


28.957 


44.550 


62.370 


82.096 


103.430126.521 


176.715 




CU. FT. 


52026 


73138 


89726 


103298 


116116 


127426 


187228 147030 


164372 


lU 


R. P. M. 


69 


97 


119 


137 


154 


169 


182 195 


218 




H, P. 


6.65 


18.700 


34.411 


52.822 


74.221 


97.741 


122.802 150.371 


210.133 



Manufacturer's Note.— The horse-power required to drive a fan 
will vary according to the manner of application. The horse- 
powers given above are 25 per cent, greater than would he required 
under ideal conditions. 

♦Condensed from the G. F. E, Co. Catalog. 



376 



TABLE 51. 

Speeds, Capacities and Horse-Povrers of "A. B. 
Plate Fans at Varying Pressures.* 



C." Steel 





«M 1 


q5 


o 


nS 


So; 


03 =: 


.5^ 


^)^ 


Q '-^ 



50 



60 



70 



80 



90 



100 



110 



120 



140 



160 



180 



200 



220 



240 



Static 

press. 



y2* 



iy2* 



.29 
oz. 



.58 
oz. 



80 



c. r. M. 

R. p. M. 
B. H. P. 



3840 
471 



54251 

665 

2.48 



36 



C. P. M. 
R. P. M. 
B. H. P. 



42 



48 



C. P. M. 

R. P. M. 

B. H . P. 

C. P. M. 
R. P. M. 
B. H. P. 



547o 

393 

^^25 

7100' 
336 

1.62 



7740 

555 

8.53 



.87 
joz._ 

6640 

816 

4.55 

~9460 

681 

6.49 



2^' 



21/2* 



1.16 
oz, 

7650 

945 

7.00 



1.44 
oz. 



31/2* 



1.73 
oz. 



109O0 

786 

9.94 



8595 

1060 

_9.81 

12250 

880 

14.00 



2.02 
oz. 



2.81 
oz. 



54 



60 



C. P. M. 

R. P. M. 

B. H. P. 

C. F. M. 
R. P. M. 
B. H. P. 



8640 

294 

_1.97 

11000" 

262 

2.52 



14050 

236 

3.21 



^ 



C. P. M. 
R. P. M. 
B. H. P. 



16600 

214 

3.80 



72 



C. P. M. 
R. P. M. 
B. H. P. 



2030O 

196 

4.64 



10020 
475 

_4.58 

12200 

416 

5.57 

"15540' 
370 

__7.08 

19850 

333 

9.05 

"23500 

303 

10.75 



122801 14150 

583 675 

8.35 12.93 



14950 

511 

10.20 

"19000" 

454 

13.00 

24300 

409 

16.65 

"28800 

371 



17200 
590 

^5.71 

21900 
525 

20.00 

'28000 

473 

^5^60 

33100 
430 



15900 

755 

18.19 

19350 

660 

J2.10 

24600 

587 

28.10 

'31450 34400 



9400 

1150 

12.85 

13400^ 

961 

18.35 

1740O 

825 

23.80 

21150 

722 

28.90 

26950] 

641 

36.85 



19.701 30.25 



84 



96 



C. P. M. 
R. P. M. 
B^H^JP. 

C. P. M. 
R. P. M. 
B. H. P. 



27400 

168 

6.^5 

345l)0 
147 

7.88 



28700 

278 

23 J^ 

38700 

238 

17.75 

4S900 

208 

22.30 



108 



C. P. M. 
R. P. M. 
B. H. P. 



42600 

131 

9.75 



120 



C. P. M. 
R. P. M. 
B. H. P. 



132 



C. P. M. 
R. P. M. 
B. H. P. 



51600 

118 

11.8 

61400 

107 

14.0 



60300 

185 

27.55 



35100 

340 

24.00 

47400 

292 

32.40 

"59800 

256 

Jl.OO 

73800 
227 

50.50 



40500 

394 

37.00 



529 
35.95 

37200 

480 

42^50 

45500 

440 

52.00 



578 
47J.0 

40700 

525 

_55.60 

49700 

481 

68.00 



10110 

1250 

16.20 

14410 

1040 

23.10 

'18700 

890 

29.90 

22800 

780 

36.50 

~29000 

693 

46.40 

'37000 

625 

59.10 

4380O 

5e8 

_70.00 

53500 

520 

85.50 



10810 

1330 

19.75 

15420 

1110 

28.10 

20010 

950 

36.60 

24350 

832 

_44.50 

31003 

740 

56.50 

39600 

665 

72.30 

46900 

605 

85.60 

57300 

555 

104.50 



54500 

337 

49.80 

"^68900 

296 

62.90 

85000 

262 

77.60 



73000 

166 

33.30 

86800 

151 

39.60 



894001103000 

204 236 

61.20[ 93.50 

1060001122200 

185 214 

72.50 111.50 



61300 

378 

_70.00 

7730O 

331 

J8.40 

95500 

293 

J.09.0 

115700 

264 

J32.1 

137400 

240 

157.0 



67000 

413 

91.70 

"84500 

362 

J15.5^ 

104300 

320 

143.0 

126500] 

289 

173. Ol 

150200' 

262 1 

206.0 



722001 

445 

115.20; 

91000 

390 

145.4 



77250 

475 

140.9 

97500 
416 

178.0 
720003 
369 

219.0 

145800 

332 

266.0 



144 



C. P. M. 
R. P. M. 
B. H. P. 



72000 



16.5 



101800 

139 

46.50 



124500 143500 

170| 197 

85. 00131. 00 1 



161000 

220 

184.0 



176000 

241 

241.0 



112500 

346 

180.0 

136100 

312 

217.50 

162000,173000 

283 802 

259. 0| 316.0 

189500,203000 

260 377 

303.0 370.5 



Manufacturer's Note.— Any of the above fans, when running at the 
speed and pressure indicated, will deliver the volume of air and require 
no more power than given in the table. 

Allowances must be made for the inefficiency of the motive power 
and for transmission losses between motive power and the fan. 

^Condensed from the A. B. C. Co. Catalog. 



377 



TABLE 52. 

Speeds, Capacities and Horse-Powers of "Sirocco*' Fans at 
Varying Pressures.* 





o 








% 


1 


m ] 


iy2 


2 


272 


3 


31/2 


4 


a> 










in. 


in. 


in. 


in. 


in. 


in. 


in. 


m. 


in. 


i^ 


1-1 , 1 


"PvQccnTQc 1 




















03 - 


5? 








.43 


.58 


.72 


.87 


1.16 


1.44 


1.73 


2.02 


2.31 


1 








oz. 


oz. 


oz. 


oz. 


oz. 


oz. 


oz. 


oz. 


oz. 






c. 


P. 


M. 


4260 


4920 


5500 


6020 


6945 


7770 


8520 


9200 


9840 


4 


24 


R. 


P. 


M. 


391 


453 


505 


554 


610 


714 


783 


846 


905 




B. 


H. 


P. 


.879 


1.348 


1.89 


2.475 


3.8 


5.32 


7.00 


8.825 


10.77 






c. 


P. 


M. 


6650 


7690 


8600 


9416 


10870 12150 


13320! 14380 


15380 


5 


80 


R. 


P. 


M. 


313 


362 


403 


443 


512 571 


625 676 


724 






B. 


H, 


P. 


1.37 


2.105 


2.96 3.868 


5.95 8.315 10.941 13.80 


16.85 






C. 


P. 


M. 


9580] 


11060 


12350 


13540 


15630 


17470 19150 


20680 


22150 


6 


36 


R. 


P. 


M. 


260 


302 


336 


369 


427 


477 523 


565 


604 






B. 


H. 


P. 


1.975 


3.03 


4.25 


5.563 


8.56 


11.96 15.72 


19.85 24.23 






C. 


P. 


M. 


13050 


15070] 


16800 


18425 


21260 


23800 26100 


28200 


30140 


( 


.42 


R. 


P. 


M. 


223 


259 


288 


316 


366 


408 447 


483 


517 






B. 


H. 


P. 


2.69 


4.126 


5.78 


7.565 


11.661 16.28! 21.43 


27.06 


33 






C. 


P. 


M. 


17000 


19700 


22000 


24100 


27820 


31100 34080 


36800 


39370 


8 


48 


R. 


P. 


M. 


196 


226 


252 


277 


320 


358 392 


424 


453 






B. 


H. 


P. 


3.51 


5.39 


7.58 


9.9 


15.22 


21.30 28.0 


35.3 


43.15 






C. 


P. 


M. 


21500 


24860 


27800 


30440 


35140 39300 


43100 


46600 


49803 


9 


54 


R. 


P. 


M. 


174 


201 


224 


246 


285 317 


348 


376 


402 






B. 


H. 


P. 


4.43 


6.81 


9.57 


12.52 


19.23 26.94 85.38 


44.70 


54.5 






C. 


P. 


M. 


26500] 30750 34300] 37650 


43400 


48570 


53220 


57500 


61500 


10 


60 


R. 


P. 


M. 


156 181 


202 222 


256 


286 


313 


338 


362 






B. 


H. 


P. 


5.46 8.42 


11.8 15.471 23.77 


38.23 


43.72 


55.2 


67.4 






C. 


P. 


M. 


32200 


37200 


41500 


45530 


52550 


58830 64450 69630 


74400 


11 


66 


R. 


P. 


M. 


142 


165 


184 


202 


233 


260 285 308 


329 






IB. 


H. 


P. 


1 6.65 


10.18 


14.3 


18.72 


28.77 


40.24 52.9 66.85 


81.5 






C. 


P. 


M. 


38300 


44240 


49400 


54130 


62500 


69900 


76600 


828C0, 8850O 


12 


72 


R. 


P. 


M. 


130 


151 


168 


185 


214 


238 


261 


282 


302 






B. 


H. 


P. 


1 7.9 


12.11 


17 


22.25 


84.2 


47.85 


63 


79.5 


97 






C. 


P. 


M. 


45000 


52000 


58100 


63600 


73500 


821O0 


90000 


973:0 


104003 


13 


78 


R. 


P. 


M. 


120 


140 


155 


171 


197 


220 


241 


261 


279 






Ib. 


H 


P. 


9.28 


14.22 


20l 26.16 


40.22 


56.2 


74 


93.35 


113.9 






C. 


P. 


M. 


52100 


60200 


67300 


73700 


85000 


95000 


1042C0 112700 


120400 


14 


84 


R. 


P. 


M. 


112 


130 


144 


158 


183 


204 


224 242 


259 






B. 


H 


P. 


10.75 


16.49 


I 23.2 


80.3 


( 46.6 


65 


85.6 108 


132 






C. 


P. 


M. 


59900 


69230 


77500 


84700 


97800 


109200,1198001129600 


138500 


15 


90 


R. 


P. 


M. 


104 


121 


135 


148 


171 


191 


209 226 


242 






B. 


H. 


P. 


12.34 


18.93 


26.6 


34.8 


53.55 


74.9 


98.5 124.2 


151.7 






C. 


P. 


M. 


67950 


78430 


81800 


96140 


114300 12450OI 136000 


147000 157300 


16 


96 


R. 


P. 


M. 


98 


114 


126 


139 


160 178 


196 


211 226 






B. 


H 


P. 


13.98 


21.5 


30.2 


39.6 


63 85.7 


112 


142 173 



*Condensed from A. B. C. Co. Catalog. 



378 



APPENDIX II 



References used Chiefly in Refrigeration 
and Ice Production 



!79 



TABLE 53. 
Freezing Mixtures,* 



Names and proportions of ingredients 
in parts 



Reduction of 
temp. deg. F. 



From To 



Total 
Reduc- 
tion of 

temp, 
deg. F. 



Snow or pounded ice 2; sodium chloride 1 

Snow 5; sodium chloride 2; ammonium chloride 1 
Snow 12; sodium chloride 5; ammonium nitrate 5 

Snow 8; calcium chloride 5 

Snow 2; sodium chloride 1 

Snow 3; dilute sulphuric acid 2 

Snow 3; hydrochloric acid 5 

Snow 7; dilute nitric acid 4 

Snow 3; potassium 4 



Ammonium chloride 5; potassium nitrate 5; 
water 16 

Ammonium nitrate 1; water 1 

Ammonium chloride 5; potassium nitrate 5; 

sodium sulphate 8; water 16 

Sodium sulphate 5; dil. sulphuric acid 4 

Sodium nitrate 3; dil. nitric acid 2 

Ammonium nitrate 1; sodium carbonate 1; 

water 1 . 

Sodium sulphate 6; ammonium chloride 4; 

potassium nitrate 2; dil. nitric acid 4 

Sodium phosphate 9; dil. nitric acid 4 

Sodium sulphate 6; ammonium nitrate 5; 

dil. nitric acid 4 





— 5 




-12 




—25 


-H32 


—40 




— 5 


+32 


—23 


+32 


—27 


+32 


—30 


+32 


—51 


+ 50 


+ 4 


+50 


+ 4 


+50 


+ 4 


+ 50 


+ 3 


+ 50 


— 3 


+50 


— 7 


+ 50 


—10 


+50 


—12 


+50 


—14 



55 

59 
62 
83 

46 
46 

46 
47 
53 

57 

60 
62 

64 



TABLE 54. 
Properties of Saturated Animonia.t 



Temp, 
deg. F. 



—40 
—35 
—30 
—25 
—20 
—15 
—10 
— 5 
± 
+ 5 
+10 
+20 
+30 
+40 
+50 
+60 
+70 
+80 
+90 
+100 



Pressure 

absolute 

lbs. per 

SQ. in. 



Heat of 
vaporization 



Vol. of 
vapor 
per lb. 
cu. ft. 



Vol. of 

liquid 
per lb. 
cu. ft. 



Wt. of 

vapor 
lbs. per 
cu. ft. 



10.69 

12.31 

14.13 

16.17 

18.45 

20.99 

23.77 

27.57 

30.37 

34.17 

38.55 

47.95 

59.41 

73.00 

88.96 

107.60 

129.21 

154.11 

182.80 

215.14 



579.67 
576.69 
573.69 
570.68 
567.67 
564.64 
561.61 
558.56 
555.50 
552.43 
549.35 
543.15 
536.92 
530.63 
524.30 
517.93 
511.52 
504.66 
498.11 
491.50 



24.38 

21.21 

18.67 

16.42 

14.48 

12.81 

11.36 

9.89 

9.14 

8.04 

7.20 

5.82 

4.73 

3.88 

3.21 

2.67 

2.24 

1.89 

1.61 

1.36 



.0234 

.0236 

.0237 

.0238 

,0240 

.0242 

.0243 

.0244 

.0246 

.0247 

.0249 

.0252 

.0254 

.0257 

.02601 

.0265 

.0268 

.0272 

.0274 

.0279 



.0411 
.0471 
.0535 
.0609 
.0690 
.0775 



.1011 
.1094 
.1243 
.1381 
.1721 
.2111 
.2577 
.3115 
.3745 
.4664 
.5291 
.6211 
.7353 



*Tayler 
tWood- 



Pocket Book of Refrigeration. 
-Thermodynamics, Heat Motors 
380 



and Refrigerating Machines. 



TABLE 55. 

Solubility of Ammonia in Water at Different Temperatures 
and Pressures. (Sims).* 

1 I'b. of water (also unit volume) absorbs the following 
quantities of ammonia. 



Absolute 


32° 


F. 


68° F. 


104° 


F. 


212° 


F. 


pressure 


















in lbs. 


















per 

sq. in. 


Lbs. 


Vols. 


Lbs. 


Vols. 


Lbs. 


Vols. 


Grms. 


Vols. 


14.67 


0.899 


1180 


0.518 


683 


0.338 


443 


0.074 


97 


15.44 


0.937 


1231 


0.535 


703 


0.349 


458 


0.078 


102 


16.41 


0.980 


1287 


0.556 


730 


0.363 


476 


0.083 


109 


17.37 


1.029 


1351 


0.574 


754 


0.378 


496 


0.088 


115 


18.34 


1.077 


1414 


0.594 


781 


0.391 


513 


0.092 


120 


19.30 


1.126 


1478 


0.613 


805 


0.404 


531 


0.096 


126 


20.27 


1.177 


1546 


0.632 


830 


0.414 


543 


0.101 


132 


21.23 


1.236 


1615 


0.051 


855 


0.425 


558 


0.106 


139 


22.19 


1.283 


1685 


0.669 


878 


0.434 


570 


0.110 


140 


23.16 


1.336 


1754 


0.685 


894 


0.445 


584 


0.115 


151 


24.13 


1.388 


1823 


0.704 


924 


0.454 


596 


0.120 


157 


23.09 


1.442 


1894 


0.722 


948 


0.463 


609 


0.125 


164 


26.06 


1.496 


1965 


0.741 


973 


0.472 


619 


0.130 


170 


27.02 


1.549 


2034 


0.701 


999 


0.479 


629 


0.135 


177 


27.99 


1.603 


2105 


0.780 


1023 


0.486 


638 






28.95 


1.656 


2175 


0.801 


1052 


0.493 


647 






30.88 


1.758 


2309 


0.842 


1106 


0.511 


671 






32.81 


1.861 


2444 


0.881 


1157 


0.530 


696 






34.74 


1.966 


2582 


0.919 


1207 


0.547 


718 






36.67 


2.070 


2718 


0.955 


1254 


0.565 


742 







TABLE 56. 
Strengtli of Ammonia Liquor.* 



Degrees 


Specific 


Percent- . 


Degrees 


Specific 


Percent- 


Baume 


gravity 


age 


Baume 


gravity 


age 


10 


1.0000 


0.0 


20 


0.9333 


17.4 


11 


0.9929 


1.8 


21 


0.9271 


19.4 


12 


0.9859 


3.3 


22 


0.9210 


21.4 


13 


0.9790 


5.0 


23 


0.9150 


23.4 


14 


0.9722 


6.7 


24 


0.9090 


25.3 


15 


0.9655 


8.4 


25 


0.9032 


27.7 


16 


0.9;389 


10.0 


26(a) 


0.8974 


• 30.1 


17 


0.9523 


11.9 


27 


0.8917 


32.5 


18 


0.9459 


13.7 


28 


0.8860 


35.2 


19 


0.9396 


15.5 


29 


0.8805 





Note.— Sp. gr. of pure anhydrous ammonia = .623 
(a) Known to the trade as "29V^ per cent." 
*Tayler. Po.cket-Book of Refrigeration. 



381 



TABLE 57. 
Properties of Saturated Sulphur Dioxide. 



(Ledoux).* 



Temp, of 


Absolute 
pressure 


Total boat 


Latent heat 


Heat of 

liquid 

from 

32 dog. F. 


Density ol 

vapor 

wt. per 

cu. ft. 


ebullition 


lbs. per 


from 


of vapor- 


deg. F. 


SQ. in. 
P -j- 144 


32 dog. F. 


ization 


oo 


5.n6 


157.43 


176.00 


—19.56 


.076 


—13 


7.23 


15S.64 


174.05 


—16.30 


.097 


— 4 


0.27 


1'>0.S4 


172.89 


—13.05 


.123 


5 


11.70 


161.03 


170.82 


— 9.79 


.153 


1-4 


14.74 


162.20 


1(^8.73 


— 6.53 


.100 


23 


18.31 


163.86 


166.63 


— 3.27 


.232 


32 


22.53 


164.51 


164.51 


0.00 


.282 


41 


27.48 


165.65 


162.38 


3.27 


.340 


50 


33.25 


166.78 


160.23 


6.55 


.407 


59 


39.03 


167.00 


158.07 


0.83 


.483 


68 


47.61 


168.00 


155.80 


13.11 


.570 


77 


56.30 


170.05) 


153.70 


16.39 


.660 


86 


66.36 


171.17 


151.40 


19.69 


.780 


05 


77.64 


172.24 


140.26 


22.98 


Am 


104 


00.31 


173.30 


147.02 


26.28 


1.046 



TABLE 5S. 
Properties of Saturated Carbon Dioxlde.f 



Temp, of 


Absolute 


Total heat 


Latent heat 


Heat of 


Density of 


ebullition 


pressure 


from 


of vapor-' 


liquid from 


vapor or 
wt. per 
cu. ft. 


deg. F. 


in lbs. 
per sq. in. 


32 dog. F. 


izatiou 


32 deg. F. 


oo 


210 


08.35 


136.15 


-37.80 


2.321 


—13 


240 


00.14 


131.65 


—32.51 


2.759 


— 4 


202 


00.88 


126.70 


—26.01 


3.265 


5 


342 


100.58 


121.50 


—20.02 


3.853 


14 


306 


101.21 


115.70 


—14.40 


4.535 


23 


457 


101.81 


100.37 


- 7.56 


5.331 . 


32 


525 


102.35 


102.35 


0.(X) 


6.265 


41 


500 


102.84 


04.52 


8.32 


7.374 


50 


680 


103.24 


85.64 


17.60 


8. 70S 


59 


768 


103.50 


75 . 37 


28 . 22 


10.356 


68 


864 


103.84 


62.08 


40.86 


12.480 


77 


0(kS 


103.05 


46.80 


57.06 


15.475 


86 


1080 


103.72 


10.28 


34.44 


21.519 



♦Kent's M. K. rookot-lU-)ok 
fl. C. S. ramphlot 1238 13. 



382 



TABLE 59. 

Pressures and Boiling Points of Liquids Available for U«e 

in Kefri^erating- Machines.* 



TABLE 60. 
Table of Calcium Brine Solution.! 



Temperature 




Pressure of vapor 




of ebullition 


Pounds per square inch absolute 


deg. F. 


Sulphur 
dioxide 


Ammonia 


Carbon 
dioxide 


Pictet 
fluid 


—40 




10.22 






—31 




13.23 






—22 


5.56 


16.95 






—13 


7.23 


21.51 


251.6 




— 4 


9.27 


27.04 


292.9 


13.5 





11.76 


33.67 


340.1 


16. a 


14 


14.75 


41.58 


393.4 


19.3 


23 


18.31 


50.91 


453.4 


22.9 


32 


22.53 


61.85 


520.4 


2(3.9 


41 


27.48 


74 . 55 


594.8 


31.2 


50 


33.26 


89.21 


676.9 


36.2 


59 


39.93 


105.99 


766.9 


41.7 


68 


47.62 


125.08 


864.9 


48.1 


77 


56.39 


146.64 


971.1 


55.6 


86 


66.37 


170.83 


1085.6 


64.1 


95 


77.64 


197.83 


12)7.9 


73.2 


104 


90.32 


227.76 


1338.2 


82.9 



Deg. 


Per cent. 












Bauine 


calcium 


Lbs. per 


Specific 


Specific 


Freezing 


Amm. 


60 deg. 


by 
weight 


cu. ft. 
solution 


gravity 


heat 


point 
deg. F. 


gage 
pressure 





O.O'X) 


0.0 


1.000 


1.000 


32.00 


47.31 


2 


1.886 


2.5 


1.014 


.988 


30.33 


45.14 


4 


3.772 


5.0 


1.028 


.972 


28.58 


43.00 


6 


5.058 


7.5 


1.043 


.955 


27. 0-) 


41.17 


8 


7.544 


10.0 


1.0.58 


.936 


25.52 


39.35 


10 


9.430 


12.5 


1.074 


.911 


22.80 


36.30 


12 


11.316 


15.0 


1.090 


.890 


19.70 


32.93 


14 


13.202 


17.5 


1.107 


.878 


16.61 


29.63 


16 


15.088 


20.0 


1.124 


.866 


13.67 


27.04 


18 


16.974 


22.5 


1.142 


.854 


10.00 


23.85 


20 


18.860 


25.0 


1.160 


.844 


4.60 


19.43 


22 


20.746 


27.5 


1.179 


.&34 


— 1.40 


14.70 


24 


22.632 


30.0 


1.198 


.817 


— 8.60 


9.96 


26 


24.518 


32.5 


1.218 


.799 


—17.10 


5 22 


28 


26.404 


35.0 


1.239 


.778 


—27.00 


.65 


30 


28.290 


37.5 


1.261 


.757 


—39.20 


8.5*' vac. 


32 


30.176 


40.0 


1.283 




—54.40 


15" vac 


34 


32.062 


42.5 


1.306 




—39.20 


4" vac. 



^Kent's M. E. Pocket-Book. 
fAm. Sch. of Cor. Dickerman-Boyer. 

383 



TABLE 61. 
Table of Salt Brine Solution.* 

(Sodium chloride). 



Degrees 

Salom- 

eter at 

60 deg. P. 


Percent, 
by wt. 
of salt 


Pounds 

of salt 

per eu. ft. 


Specific 
gravity 


Specific 
heat 


Freezing 

point 
deg. F. 


Amm. 

gage 

pressure 





0.00 


0.000 


1.0000 


1.000 


32.0 


47.32 


5 


1.25 


0.785 


1.0090 


.990 


30.3 


45.10 


10 


2.50 


1.586 


1.0181 


.980 


28.6 


43.03 


15 


3.75 


2.401 


1.0271 


.970 


26.9 


41.00 


20 


5.00 


3.239 


1.0362 


.960 


25.2 


38.96 


25 


6.25 


4.099 


1.0455 


.943 


23.6 


37.19 


30 


7.50 


4.967 


1.0547 


.926 


22.0 


35.44 


85 


8.75 


5.834 


1.0640 


.909 


20.4 


33.69 


40 


10.00 


6.709 


1.0733 


.892 


18.7 


31.93 


45 


11.25 


7.622 


1.0828 


.883 


17.1 


£0.33 


50 


12.50 


8.542 


1.0923 


.874 


15.5 


28.73 


55 


13.75 


9.462 


1.1018 


.864 


13.9 


27.24 


60 


15.00 


10.389 


1.1114 


.855 


12.2 


25.76 


65 


16.25 


11.384 


1.1213 


.848 


10.7 


24.46 


70 


17.50 


12.387 


1.1312 


.842 


9.2 


23.16 


75 


18.75 


13.396 


1.1411 


.835 


7.7 


21.82 


80 


20.00 


14.421 


1.1511 


.829 


6.1 


20.43 


85 


21.25 


15.461 


1.1614 


.818 


4.6 


19.16 


90 


22.50 


16.508 


1.1717 


.806 


3.1 


18.20 


95 


23.75 


17.555 


1.1820 


.795 


1.6 


16.88 


100 


25.00 


18.610 


1.1923 


.783 


0.0 


15.67 



TABLE 62. 

Horse-Po\Ter Required to Produce One Ton of Refrigeration.! 

Condenser pressure and temperature. 





P 


103 


115 


127 


139 


153 


168 


184 


2C0 


218 


T 


65 


70 


75 


80 


85 


90 


95 


lOO 


105 




—20° 


1.0584 


1.1304 


1.2051 


1.2832 


1.3611 


1.4427 


1.5251 


1.609O 


1.6910 


—15 


.9972 


1.0694 


1.1450 


1.2221 


1.3001 


1.4101 


1.4609 


1.5458 


1.6300 


S 9 


—10 


.9026 


.9777 


1.0453 


1.1183 


1.1926 


1.2602 


1.3471 


1.4352 


1.5093 


g]3 


— 5 


.8184 


.8833 


.9537 


1.0230 


1.0935 


1.1679 


1.2437 


1.3209 


1.3961 


A 16 





.7352 


.8008 


.8648 


.9328 


1.0019 


1.0718 


1.1467 


1.2194 


1.2547 


f^ 20 


5 


.6665 


.7312 


.7946 


.8593 


.9278 


.9978 


1.0656 


1.1381 


1.2121 


2 24 


10 


.5915 


.6629 


.7257 


.7894 


.8545 


.9205 


.9911 


1.0595 


1.1294 


n 28 


15 


.5410 


.5998 


.6641 


.7276 


.7924 


.8553 


.9224 


.9943 


1.0603 


•S 39 


20 


.4745 


.5340 


.5923 


.6716 


.7148 


.7796 


.8420 


.9031 


.9736 


25 


.4103 


.4659 


.5227 


.5804 


.5992 


.7022 


.7667 


.8289 


.8922 


V> 45 


30 


.3509 


.4056 


.4612 


.5178 


.5755 


.6353 


.6944 


.7590 


.8172 


« 51 


35 


.3005 


.3546 


.4101 


.4666 


.5214 


.5804 


.6398 


.7009 


.7629 



Note.— The above figures are purely theoretical. 
50 per cent, must be added. 

*Am. Sch. of Cor. Dickerman-Boyer. 
tDe La Vergne Catalog. 



In practice about 



384 



TABLE 63. 



Cubic Feet of Ammonia Gas per Minute to Produce One Ton 
of Refrigeration per Day.* 

Condenser pressure and temperature. 







Press. 


103 


115 


127 


139 


153 


168 


185 


200 


218 


^3 
03 


Press. 


Temp. 


65° 


70° 


75° 


80° 


85° 


90° 


95° 


100° 


105° 


2 


4 


—20° 


5.84 


5.90 


5.96 


6.03 


6.06 


6.16 


6.23 


6.30 


6.43 


S 4^ 


6 


—15° 


5.35 


5.40 


5.46 


5.52 


5.58 


5.64 


5.70 


5.77 


5.83 


c^E 


9 


—10° 


4.66 


4.73 


4.76 


4.81 


4.86 


4.91 


4.97 


5.05 


5.C8 


n^ 


13 


— 5° 


4.09 


4.12 


4.17 


4.21 


4.25 


4.30 


4.35 


4.40 


4.44 


«-i 3? 


16 


0° 


3.59 


3.63 


3.66 


3.70 


3.74 


3.78 


3.83 


3.87 


3.91 


03 a, 


20 


5° 


3.20 


3.24 


3.27 


3.30 


3.34 


3.38 


3.41 


3.45 


3.49 


24 


10° 


2.87 


2.90 


2.93 


2.96 


2.99 


3.02 


3.06 


3.09 


3.12 


^" 


28 


15° 


2.59 


2.61 


2.65 


2.68 


2.71 


2.73 


2.76 


2.80 


2.82 


fcfl 


33 


20° 


2.31 


2.34 


2.36 


2.38 


2.41 


2.44 


2.46 


2.49 


2.51 


«M 


39 


25° 


2.06 


2.08 


2.10 


2.12 


2.15 


2.17 


2.20 


2.22 


2.24 


« 


45 


30° 


1.85 


1.87 


1.89 


1.91 


1.93 


1.95 


1.97 


2.00 


2.01 




51 


35° 


1.70 


1.72 


1.74 


1.76 


1.77 


1.79 


1.81 


1.83 


1.85 



TABLE 64. 
Table of Refrigerating Capacities.f 



Size of buildiner 




Number of 


cu. ft. per 


ton oi 


I refrigera- 










tion 


at temperatures given 


Dimen- 
sions? of 


Con- 
tents 


Sur- 
face 


Ratio 
cu. ft, 


Temperatures 


building 


cu. ft. 


m sq. 
ft. 


to sq. 
ft. 


0^ 


8° 


16° 


24° 


32° 


40° 


48° 


5x4x5 


100 


130 


1.3 


900 


1100 


1300 


1500 


1700 


1900 


2100 


8x10x10 


800 


520 


.65 


1800 


2200 


2600 


3000 


3400 


3800 


4200 


25x40x10 


lOOOO 


3300 


.33 


3600 


4400 


5200 


6000 


6700 


7600 


8400 


20x50x20 


20000 


4800 


.24 


4860 


5940 


7020 


8100 


9180 


10260 


11340 


40x50x20 


40000 


7600 


.19 


6300 


7700 


9100 


10500 


11900 


13300 


14700 


60x50x20 


60000 


10400 


.17 


6840 


8360 


9880 


1140O 


12920 


14440 


15960 


80x50x20 


80000 


13200 


.165 


7200 


8800 


10700 


12000 


13600 


15200 


16800 


100x50x20 


100000 


16000 


.16 


7200 


8800 


10400 


12000 


13600 


15200 


1680O 


100x100x20 


200000 


28000 


.14 


8100 


9900 


11700 


1.3000 


15.300 


17100 


18900 


100x100x40 


400000 


36000 


.09 


1.3050 


15950 


18850 


21750 


24650 


27550 


30450 


100x100x60 


600000 


44000 


.073 


16200 


19800 


23400 


27000 


30600 


3420O 


37800 


100x100x80 


800000 


52000 


.065 


18000 


22000 


26000 


30000 


34000 


38000 


42000 


lOOxlOOxlOO 


1000000 


60000 


.06 


19350 


23650 


27950 


32250 


36550 


40850 


45150 



*Featherstone Foundry and Machine Co. Catalog. 
tTayler. P. B. of R. 



385 



o 
u 



1^S| 














;|J 


;^ 


^ 


o 


on 


f- 


cs 


CO 


O 


tH 


CO 


<N 


C5 


CO 


t^ 


i> 


J> 


o 


CO 


lO 






















o 


1— t 


















o'S^ 


^ 


















° a 




















t>c«, 




















Daily 

eratin 

pense 


8 


s 


T-H 


CO 




s 

CO 


8 

cs 




1> 


T-; 


tH 


CO 


<N 


(M 


Thi 




O 


iO 


a« 


ee- 


















o « 




















^ 





















a '^ f^ 



68 






in 

^LC ft 






.8 



c 
'5]" 






O GJ 

E-ift 



SSS^SSBS 



S S B B 2 



_oococooo»^o 
cccox c:c-)0o<mc»'* 

T— 1-- !M CJ CO 



8 8 8 8 g § 8 8 

COCOCOCOTjlTiHCOCO 



C<lC<JC<IC<lCOCOrJirfi 



8 8 8 8 



c<i cq CNJ 



O ir^ O O 
;o 1- w c^a 



8 


8 


s 


8 


g 


s 


8 


8 


8 


CO 


CO 


CO 


CO 


"^ 


■^ 


CO 


Oi 


05 


C3 


;j 


- 


3 


- 


- 


- 


- 


- 


CO 


CO 


CO 


CO 


CO 


CO 


•* 


CO 


CO 



§ 


g 


g5 


g 


8 


s 


8 


8 


8 




ia 


IC 


IC 


«o 


C5 


s 


tH 


r-i 




- 


:: 


>• 


- 


^» 


3 


s 


2 


CO 


CO 


CO 


CO 


CO 


CO 


^ 


CO 


CO 



15 


;h 




si 


O) 


s: 


G 


CJ 


x: 


^ 


« 


"^ 


C3 


UL 


S 


f\1 


TJ 


T- 


a 


P 


03 






O 


>> 


C 


Ut 


"^ 


'a 


■4-3 


a 


c 


3 


c 


O 


w 


^ 


Q) 




n 


« 




c 


" 


o 


(V 


4J 






^ 




03 


a 




•*-* 


m 


08 


^ 

b 


1! 



3SG 



Table 66. 

Temperatures to AVhich Ammonia Gas Is Raised by 
Compression. * 



Tempera- 


Absolute 




Absolute suction pressure 




ture of 
suction 


condensing 
pressure 














20 


25 


80 


35 


40 


45 


deg. F. 


90 


199 


165 


138 


116 


98 


83 




110 


232 


196 


166 


145 


126 


109 




130 


261 


222 


193 


169 


150 


132 




150 


285 


246 


216 


191 


171 


153 




160 


296 


257 


226 


202 


181 


163 


5 deg. F. 


90 


266 


172 


145 


123 


104 


89 




110 


239 


203 


174 


151 


132 


115 




130 


268 


230 


200 


176 


156 


139 




150 


293 


254 


223 


198 


178 


160 




160 


805 


265 


234 


209 


188 


170 


10 deg. F. 


90 


213 


178 


151 


129 


110 


96 




110 


247 


210 


181 


158 


139 


122 




130 


275 


237 


207 


183 


163 


145 




150 


301 


262 


231 


205 


185 


167 




160 


313 


273 


241 


216 


195 


176 


15 deg. F. 


90 


221 


185 


158 


135 


117 


101 




110 


254 


217 


188 


164 


145 


128 




130 


283 


245 


214 


191 


170 


152 




150 


309 


269 


238 


213 


192 


173 




160. 


321 


281 


249 


223 


202 


183 


20 deg. F. 


90 


228 


192 


164 


141 


123 


106 




110 


262 


224 


195 


171 


150 


134 




130 


291 


252 


222 


197 


176 


158 




150 


317 


277 


245 


220 


198 


180 




160 


329 


288 


256 


230 


209 


190 


25 deg. F. 


90 


235 


199 


171 


148 


129 


111 




110 


269 


230 


200 


178 


155 


140 




130 


299 


259 


229 


204 


183 


165 




150 


325 


284 


253 


227 


205 


187 




160 


838 


296 


264 


237 


216 


197 


30 deg. F. 


90 


242 


206 


177 


154 


134 


118 




110 


277 


239 


208 


184 


164 


147 




130 


807 


267 


236 


211 


190 


171 




150 


334 


292 


260 


234 


•212 


193 




160 


346 


804 


271 


245 


223 


203 


35 deg. F. 


90 


249 


213 


182 


160 


141 


124 




110 


286 


246 


215 


191 


170 


153 




130 


315 


274 


243 


217 


196 


178 




150 


841 


300 


268 


241 


219 


200 




160 


354 


812 


279 


252 


230 


210 



^Tayler. P. B. of R. 



387 



o 




1— ( 


i 




rH 




1 1 


CO 




r-t 




8 

d 




o 

1-H 


s 


53 


i 


00 

oi 






00 


iH 


00 

1-H 

d 


1— ( 

00 

rH 


s 


so 


I— t 
-<* 
I— 1 


in 










d 


o 

r-l 
rH 


s 


1— 1 




1— 1 


in 

CO 




o> 

CO 


rH 

!— 1 


d 


CO 
rH* 


s 




8 

tH 


OS 


CO 1 1 lO 
1 


in 

iH 


d ^ 


lo 
■^ 


o 


i 


tH 


00 


1—1 


o 

1-H 
CO 


lH 


2 I 


5 






CO 

d 

T— 1 

r-l 


05 
CO* 




CO 


rH 


S3 

d 


.-J 


s 


CO 






o 

rH 






lH 


d 


1—1 


s 




<M* 


00 


in 

CO 


i 


d 


tH 


00 CO 

*■ IS 




00 




Oi 


CO 


in 
in 


(M 


iH 


d 


O 


g 


1 






m 


i 


00 

00 

tH 


s 

I-H 
1-» 


d 


rH 

1—1 


s 


T-H 


o 

CO 


CO 

1— f 






CO 

d 


in 

1-H 
I-H 

tH 


d 


1—1 

rH 
I-H 






00 

1—1 


lO 


i-H 


o 

00* 


C5 

d 


1 


rH 


! 


in 


CO 




05 

CO 
tH 


05 

in 


o 

o* 


in 

00* 


r-^ 


1 

i 

1 


rH 


o o 1 o 1 o 1 o 


1 = 


o 


T-i 


1 


rH 


a 

S3 

cq 

00 

a 


s 

d 

tH 

S 

! 
1 


T 

Ho 

ft 






M 
1 

1 

■* 

UO 


1— t 

d 

^ 1 
c* 


o 

1 1 

i 

. 1 


5 

si 

1 


1 

1 

§ ? 




o 

1 

1 

1 

H 

UO 


a 

Is 

Si 1 

i ^ 


o 

M 

1 

in 

iH 

1 

io 
i 

Q 


Is 

GQ 

1 ' 

5 g 


o 

+ 

1 

■1 

Q 


1 

.s 


03 

o 


1 


«3 s- 

03 
C3 


(•li o09) *0 oS*ST 
•ossy 'inaqo -g 'n 


iS 


JIAB 


i3 ogioi 


>(IS 





388 



TABLE 68. 
Time Required to Freeze Ice in Cells or Cans, (a) (Slebert),* 













Thickness 


in inches 










Temp. 


























deg. F. 


1 


2 


3 


4 


5 


6 


7 


8 


9 


10 


11 


n 


10 


0.32 


1.28 


2.86 


5.10 


8.00 


11.5 


15.6 


20.4 


25.8 


31.8 


38.5 


45.8 


12 


0.35 


1.40 


3.15 


5.60 


8.75 


12.6 


17.3 


22.4 


28.4 


35.0 


42.3 


50.4 


14 


0.39 


1.56 


3.50 


6.22 


9.70 


14.0 


19.0 


25.0 


31.5 


39.0 


47.0 


56.0 


16 


0.44 


1.75 


3.94 


7.00 


11.00 


15.8 


21.5 


28.0 


35.5 


43.7 


53.0 


63.0 


18 


0.50 


2.00 


4.50 


8.00 


12.50 


18.0 


24.5 


32.0 


40.5 


50.0 


60.5 


72.0 


20 


0.58 


2.32 


5.25 


9.30 


14.60 


21.0 


28.5 


37.3 


47.2 


58.3 


70.5 


84.0 


22 


0.70 


•?.80 


6.30 


11.20 


17.50 


25.2 


34.3 


44.8 


56.7 


70.0 


84.7 


ICO.O 


2i 


0.88 


3.50 


7.86J14.00 


21.00 


31.5 


42.8 


56.0 


71.0 


87.5 


106.0 


126.0 



(a; Time required from one wall, for plate ice, two times the above values. 



TABLE 69. 
Standard Size.s of Ice Cans.f 



• Size of 


Size of 


Size of 


Inside 


Outside 


Size of 


cake, in 


top, 


bottom. 


depth, 


depth. 


band, 


pounds 


inches 


inches 


inches 


inches 


inches 


50 


8x8 


71/2x7% 


31 


32 


y4XlV2 


100 


8x16 


714x1514 


31 


32 


V4X11/2 


200 


111/2x221/2 


1014x211/2 


31 


32 


14x2 


300 


111/2x221/2 


101/2x211^ 


44 


45 


V4X2 


400 


Ili/2x22y2 


101/2x2114 


57 


58 


¥4x2 



TABLE 70. 
Cold Storage Temperatures for Various Articles.* 



Article 



Temp, 
deg. 



Apples 

Asparagus 

Bananas 

Beans (dried) __ 
Berries (fresh)__ 
Buckwheat 

flour 

Butter 

Cabbage 

Cantaloupes _._ 

' Celery 

Cheese 

Chocolate 

Cider 

Claret 

Corn (dried) 

Cranberries 

Cream 

Cucumbers 

Dates 

Eggs 

Figs 

Fish (fresh) .__ 
Fish (dried) ___ 



32-.36 
34 
40-45 
32-40 
36-40 

40 
32-38 

34 

40 
32-34 
32-33 

40 
30-40 
45-50 

35 
34-36 

35 

39 

55 
33-35 

55 
25-30 

35 



Article 



Temp. 

deg. 

F. 



Fruits 


26-55 


Fruits (dried)-- 


35-40 


Fruits (canned) 


35 


Furs (un- 




dressed) 


35 


Furs (dressed) _ 


25-32 


Game (frozen) — 


25-28 


Game (to 




freeze) 


15-28 


Grapes 


36-.38 


Hams 


.30-35 


Hops 


33-40 


Honey 


45 


Lard 


34-45 


Lemons 


36-40 


Meat (canned)-- 


35 


Meat (fresh)._.. 


34 


Meat (frozen) __ 


25-28 


Milk 


32 


Nuts 


35 


Oat meal 


40 


! Oil 


35 


1 Oleomargarine . 


35 


• Onions 


34-40 



Article 



Temp. 

deg. 

F. 



(in 



(in 



Oranges 
Oysters 
Oysters 

tubs) 
Oysters 

shells) 

Peaches 

Pears 

Peas (dried) . 

Pork 

Potatoes 

Poultry 

(frozen) _._. 
Poultry (to 

freeze) 

Sugar, etc. .. 

Syrup 

Tobacco 

Tomatoes __. 
Vegetables __. 
Watermelons 
Wheat flour . 

Wines 

Woollens, etc. 



45-50 
33-35 

25 



45-55 

34-36 

40 

34 

36-40 

28-30 

18-22 

40-45 

35 

35 

36 

34-40 

34 

40 

40-45 

25-32 



♦Tayler. P. B. of R. 
fAs adopted by the Ice Machine Builders' 

389 



Association of the U. S. 



APPENDIX III 



391 



Tests of House Heating; Boilers. 

The following extract from a series of tes-ts on a Num- 
ber S-48-7 Ideal Sectional Boiler from the reports of the 
American Radiator Company's Institute of Thermal Re- 
search, Buffalo, New York, will be of interest. 

Size of grate.. 48x64% in. Grate area „ 21.6 sq. ft. 

Heating surface— total 800.0 sq. ft. 

Hard Hard Hard 

0— Fuel used in tests Coal Coal 

1— No. of boiler S-48-7 S-48-7 

2— Duration of test hours 8:00 7:00 

4— Fuel burned during test, lbs 1360.00 1344.00 

5— Fuel per hour, lbs. 170.00 192.00 

6— Fuel per sq. ft. grate per hour, lbs 7.90 8.95 

7— Stack temperature, degrees Fahrenheit 750.00 725.00 

8 — Evaporation per sq. ft. of heating surface 

per hour, lbs. 4.97 5.60 6.24 

9— Evaporative power available — lbs. of water 

per lb. of coal 8.80 8.75 8.77 

10— Boiler-power (evaporation per hour) — lbs. 

(item 5 X item 9) 1496.00 1680.00 1562.00 

11— Capacity— sq. ft. (item 10 -r- 0.22) 6800.00 7640.00 7100.00 

12— Capacity— sq. ft. (item 10 -^ 0.25) 5980.00 6720.00 6250.00 

Catalog rating _.570O sq. ft. 



Coal 

S-48-7 
8:00 
1434.00 

178.20 
8.35 

600.00 



The accompanying figure shows the combustion chart 
as developed for this same boiler. The tests were run to 

find the evaporative power and ca^ 
pacity with varying amounts of 
coal burned per hour. Coal was 
fired at regular intervals and the 
steam pressure was maintained at 
two pounds gage on the radiation. 
Line 11 gives the capacity in 
square feet of radiation including 
mains and risers, at the rate of 
.22 pound of steam per square 
foot per hour. Line 12 gives the 
capacity at .25 pound of steam per 
square foot per hour. In average 
service about one-third of these 
quantities of coal would be burned. The catalog rating is 
based upon burning 167.5 pounds of coal per hour and an 
evaporation of 8.5 pounds of water per pound of coal (rates 
of combustion and evaporation that seem justifiable). As 



^1 


leoo 

« 1500 

1 1400 
« 1300 
^«200 

2 noo 

'^ 1000 
O 900 
g 800 

2 -"/ 

600 
500 


















;/ 


9 
















y 
















^ 


'Basis 












J 




Ratine 










/ 
















} 
















y 








5-48- 


7 




/ 


• 














/ 


/ 
















/ 






















































fiARO 


100 125 150 175 2 
COAL BURNED PER HOUR (POUN 


)0 
DS) 



392 



will be seen from lines 5 and 9 the actual amount of coal 
burned -and the actual evaporation in each test exceed this 
figure. Multiplying" 167.5 by the assumed evaporative rate 
of 8.5 and dividing by .25 = 5700 square feet. Comparing 
with column 2, line 5 times line 9 divided by .25 gives 6720 
square feet, which is above /the catalog rating. Test number 
two compared with test number one shows that by in- 
creasing the amount of coal from 170 pounds to 192 pounds 
per hour increases the boiler capacity 740 square feet. 



395 



Data Required for Estimating Plain Hot Water or Steam 

Plants. 



Name 

of 
room 





Size of 






« 


Radiators 


4^ 


room 


^ 


to 


1^ 


Steam or water 


x2 
« a 




2 


ft 


ft 






















^^. 








a 
n 


£ 
















O 


















4i 


»-. 






'^v. 


^ 


O) 


xi 


« 






■4-3 


t5S 


£ 


a 

523 


O) 


^ 


o o 

M ft 


c 
o 






5 






5 


Q.2 


'5 


>> 


5 



Remarks: 
Cold floor, 
ceiling, etc. 






Date 191_.- 

Owner of building Address 

Architect Address 

Kind of building Location 

Nearest freight station 

Temperature in living rooms Kind of fuel used 

Height of cellar Size of smoke flue x 

Items to Estimate on. 



.m. 



Boiler and foundation... 

Smoke pipe and damper 

Thermometers and pressure and safety gages. 

Draft regulation 

Firing tools 

Filling and blow-off connection 

Pipe and fittings 

Sq. ft. of radiation 

Cut-off valves and radiator valves 

Air valves 

Radiator wall shields 

Temperature control 

Humidifying apparatus 

Floor and ceiling plates 

Hangers 

Expansion tank 

Cold air ducts, stack boxes and registers 

Pipe covering 

Bronzing 

Labor of installation 

Freight and cartage 

Per cent, of profit 

Total bid __ 

Submitted by 



394 



INDEX 



Absolute pressure, 12 
temperature, 12 

Absorbers, 300 

Absorption system of refrigeration, 
294 
and compression system compared, 

302 
system condensers for, 299 
system, elevation of, 296 
system pumps for, 301 

Accelerated systems hot water, 95 

Adaptation of district steam to pri- 
vate plants, 267 

Advantages of vacuum systems, 142 

Air, amount to burn carbon, 35 
circulation furnace system, 53 
circulation within room, 76 
composition, 16 
duct, fresh, 59 

exhausted, actual from nozzle, 188 
exhausted per hour plenum system, 

170 
h. p. in moving, 192 
h. p. in moving, table, 186 
humidity of, 25 
leakage, heat loss by, 43 
moisture required by, 30 
needed plenum system, 172 
per person, table, 24 
required as heat carrier, 54 
temperature at register, 56 
valves, 112 

velocities of in convection, 31 
velocities, measurement of, 32 
velocities, plenum system, table, 

172, 184 
required, ventilating purposes, 21 
washing and humidifying, 167 

Ammonia for one-ton refrig., 385 
solubility in water, 381 
strength of liquor, 381 

Anchors, types of, 221 

Anemometer, 32 

Appendix 
table 1 squares, cubes, etc., 328 
table 2 trigonometric functions, 

334 
table 3 equivalents of units, 334 
table 4 properties of steam, 335 
table 5 Naperian logarithms, 338 
table 6 water conversion factors, 

338 
table 7 volume and wt. of dry air, 

339 
table 8 weight of pure water, 340 
table 9 boiling points of water, 

342 
table 10 weight of water in air, 342 
table 11 relative humidities, 343 



table 12 properties of air, 344 
table 13 dew points of air, 345 
table 14 fuel values Am. coals, 348 
table 15 cap. of chimneys, 349 
table 16 equalization of smoke 

flues, 350 
table 17 dimensions of reg., 350 
tables 18, 20 cap. of fur., 351, 352 
table 19 cap. pipes and reg., 351 
table 21 area vertical flues, 352 
table 22 sheet metal dim., 353 
table 23 weight of G. I. pipe, 354 
table 24 sp. ht., etc., of substances, 

355 
tables 25, 26 water pressures, 356 
table 27 wrought iron pipes, 357 
table 28 expansion of pipes, 358 
table 29 tapping list of rad., 358 
table 30 pipe equalization, 359 
table 31 cap. hot water risers, 360 
table 32 cap. steam pipes, 360 
table 33 cap. hot water pipes, 361 
table 34 cap. hot water mains, 361 
tables 35, 36 sizes of steam mains, 

362, 363 
table 37 friction in pipes, 364 
table 38 grav. and vac. returns, 865 
table 39 expansion tanks, 365 
table 40 sizes of flanged fittings, 

366 
table 41 pipe fittings, 366 
table 42 friction in air pipes, 367 
table 43 temp, for testing steam 

plants, 370 
table 44 spec, for boilers, 371 
table 45 heat trans, through pipe 

covering, 372 
table 46 factors of evap., 373 
table 47 heat in feed water, 373 
table 48 sizes of Vento heater, 374 
table 49 steam used by engines, 375 
tables 50, 51, 52 speeds, cap. and 

h. p. of various fans, 376, 

378 
table 53 freezing mixtures, 380 
table 54 properties of ammonia, 

380 
table 55 sol. of ammonia in water, 

381 
table 56 strength of ammonia 

liquor, 381 
table 57 prop, of sulphur dioxide, 

382 
table 58 prop, of carbon dioxide, 

382 
table 59 boiling pts. of liquids, 383 
table 60 calcium brine sol., 383 
table 61 salt brine sol., 384 
table 62 horse-power for refrig., 384 



95 



396 



INDEX 



table 63 ammonia for one-ton 

refrig., 385 
table 64 refrigeration caps., 385 
table 65 cost of ice making, 386 
table 66 temperature of ammonia, 

387 
table 67 hydrometer scales, 388 
table 68 time to freeze ice, 389 
table 69 sizes of ice cans, 389 
table 70 temp, for cold storage, 389 

Application of formula in furnace 
heating, 62 
of plenum system, 200 

Area of ducts, plenum system, 172 
of chimney determination of, 35 
of grate, 59 

Arrangement of Vento heaters, 161 
of coils, plenum system, 160 

Automatic vacuum system, 149 
valves, 149 

Basement plans plenum system, 203 
Belvac thermofiers, 148 
Blowers and fans, speeds of, table, 
197 

work, Carpenter's rules, 194 
Boilers, 251 

feed pumps, 249 

capacity and number of, 255 

radiation supplied by, 252 

plant capacity of, 255 

steam, 108 

tests of, 392 
Boihng point of water, table, 342 
Boiling points of liquids, 383 
Brine cooling system, cap. of, 315 
British thermal unit, 10 
B. t. u. lost in plenum system, 176 
Building materials, conductivities of, 
40 

Calcium brine solution, 383 
Calculating chimney areas, 35 

heat loss, 45-46 
Calorie, 10 
Carbon amount of air to burn, 35 

dioxide, 18 

dioxide per cent., table, 19 

dioxide tests for, 19 
Carpenter's practical rules, 194 
Cast radiators, 103 

surfaces, plenum system, 161 
Centrifugal pumps, 247 
Check valve, ill 

Chimney area, determination of, 35 
Chimneys, 36 

capacity of, table, 349 
Circulating system for refrigerating, 
302 

duct in furnace design, 72 

water to condense steam, 237 
Classification of radiators, 104 
Coal, fuel values of, table, 348 
Coils, arrangement of in pipe heater, 
180 



arrangement of Vento in stacks, 
182 

heat transmission through, 174 

heat transmission through Vento, 
table, 177 

SQ. ft. for cooling, 311 

surface, plenum system, 173 

temp, leaving Vento, table, 180 
Cold air system of refrigeration, 284 
'Combination systems, 110 

heaters, 70 
Comparison of furnace and other 

systems, 51 
Composition of air, 16 
Compression and absorption system 
compared, 302 

systems, condensers for, 289 

system of refrigeration, 286 
Condensation, dripping from mains, 
267 

return to boilers, 133 
Condenser, concentric tube, 289 

enclosed, 290 

for compression systems, 289 

submerged, 290 

for exhaust steam, 238 

heating surface in, 239 
Conduction, 14 

of building material, table of, 40 
Conduits, district heating, 212 
Convection, 15 

Conversion factors for water, 338 
Coolers for weak liquor, 301 
Cost of heating from central sta- 
tion, 258 

of ice making, 316, 386 

Data for estimate, 394 
Data, table for plenum system, 202 
Design, hot water and steam, 114 
Determination of pipe sizes, 121 
Dew point, influence of en refrigera- 
tion, 305 
Dew points of air, 345 
Direct radiation, tapping list, table, 

358 
Dirt strainer, Webster, 147 
District heating 

adaptation to private plants, 267 

amount of radiation supplied by 
one horse-power exhaust steam, 
237 

amount of radiation supplied, 237 

amount of radiation supplied by 
reheater, 241 

application to typical design, 268 

boiler feed pumps, 249 

boilers, 251 

by steam, 264 

capacity of boiler plant, 255 

centrifugal pumps, 247 

circulating pumps, 244 

city water supply, 249 

classification, 229 

condensation from mains, 267 



INDEX 



397 



conduits, 212 

cost of heating, 258 

cost, summary of tests, 260 

design for consideration, 222 

dripping condensation from mains, 

267 
diameter of mains, 265 
economizer, 253 
exhaust steam available, 223 
future increase, 231 
general application of design, 268 
heat available in exhaust steam, 

225 
heating by steam, 264 
heating surface in reheater, 239 
high pressure steam heater, 2i4 
hot water systems, 229 
important reheater details, 242 
layout for conduit mains, 218 
power plant layout, 259 
pressure drop in mains, 231, 265 
radiation in district, 231 
radiation supplied by 1 h. p. of ex. 

St., 237 
radiation supplied by economizer, 

253 
radiation supplied per boiler h. p., 

252 
references on district heating, 270 
regulation, 263 
reheater details, 242 
reheater for circulating water, 238 
reheater tube surface, 241 
scope of work, 209 
service connections, 235 
steam available for heating, 236 
systems classified, 229 
typical design, 222 
velocity of water in mains, 234 
water per hour, as heating medium, 

230 
water to condense one pound of 

steam, 237 
Division of coils, plenum sys., 162 
Ducts, furnace, cold air, 59 
plenum system, 165-166 
recirculating, 72 

Economizers, 253 

radiation supphed by, 253 

surface, 2.55 
Efficiency of plenum coils, table, 175 
Electrical heating, 279 

formulas used in, 279 

future of, 282 

references, 282 
Electric pumps, 137 
Engine, size of, 197 
Equivalents of units, 334 
Evaporators for refrig., 292 
Exchangers, 301 
Exhaust steam available in district 

plants, 223 
Exhaust steam condenser, 238 



Expansion joints, 218 

tanks, 113, 365 
Exposure heat losses, table, 43 

Factors of evaporation, 373 
Factor table, velocity and vol., 188 
Fans and blowers, 155 
drives, 195 
housings, 157 
power of engine for, 197 
size of parts, 195 
speed of, 196 
Fire places, stoves, etc., 153 
Fittings, steam and hot water, 110, 

366 
Floor plans for furnace heating, 

64-66 
Floor plans for plenum sys., 203-205 
Formulas, empirical for radiation, 
117 
' Freezing mixtures, 380 

Fresh air duct, 59-71 
i Fresh air entrance to bldgs., 159 
i Friction diagrams, 368, 369 

in pipes, 364 
I of air in pipes, 367 
i Fuel values of Am. coals, table, 348 

Furnace, 
! air circulation within room, 76 

foundations, 71 
I heating, 51 
j location, 71 
; selection, 67 

j Furnace system, air circulation, 53 
! air required as heat carrier, 54 
i circulating duct in, 72 
design of, 62 
essentials of, 52 
fan in, 77 

fresh air duct in, 71 
grate area in, 59 
gross register area in, 57 
heat stacks, sizes of, 57 
heating surface in, 61 
leader pipes in, 59, 73 
net vent register in, 56 
plans for, 64 

points to be calculated in, 53 
registers, temperatures in, 56 
stacks or risers in, 74 
three methods of installation, 55 
vent stacks, 76 

Gage pressure, 12 

Gallon degree calculation, 315 

Gate valve. 111 

Generators, 298 

Globe valve. 111 

Grate area, boilers and heaters, 123 

Grate area for furnaces, 59 

Greenhouse heating, 118 

Gross register area, 51 

Hammer, water, 133 



398 



INDEX 



Heat given off by persons, lights, 
etc., 49 

latent, 13 

measurement of, 10 

mechanical equivalent of, 13 

stacks, sizes of, 57, 74 
Heaters, hot water, 108 
Heating, district, cost of, 258 
Heating surface in coils, plenum sys- 
tem, 159 

Heating sur., in economizer, 254 

in furnace system, 61 

in reheater, 239 

per h. p. in reheater, 241 
Heat loss, 43, 44, 45, 46 

calculation of, 45 

calculation for refrig., 308 

chart, 81 

combined, 47 

for a 10 room house, table, 63 
High pressure heater, 244 
High pressure steam trap, 134 
Horse-power, in moving air, 192 

of engine for fan, 197 

required to move air in plenum sys- 
tem, 193 
Hot air pipes, cap. of, table, 351 

water heaters, 108 

water pipes, capacity of, table, 361 

water radiators, 106 

water risers, cap. of, table, 360 

water system, 85 

water used in indirect coils in ple- 
num system, 183 
Hot water and steam heating, 

accelerated systems, 95 

calculation of rad. sur. for, 114 

classifications, 87 

connection to radiators, 124 

determination of pipe sizes, 121 

diagrams for, 91 

empirical formula for, 117 

expansion tank for, 113 

for district heating, 229 

fittings, 110 

grate area for heaters, 123 

greenhouse radiation, 118 

layout, 128 

location of radiators for, 124 

parts of, 85 

pitch of mains for, 124 

principles of design of, 114 

second classification of, 88 

suggestions for operating, 137 

temperature, table. 120 
Humidity of the air, 25 
Humidities, relative, table, 343 
Hydrometric scales, 388 
Hygrodeik, 27 
Hygrometer, 26 
Hygrometric chart, 29 



Ice making, 
capacity, calculation, 
costs of, 316 



314 



Indirect radiators, 88 

Insulation of steam pipes, 131, 309 

'K' values for pipe coils, table, 174 
*K' values for Vento coils, 177 

Latent heat, 13 

Layout for furnace system, 64 

for hot water heating plant, 128 

for plenum system, 163 

of power plant, 259 

main and riser, 131 

steam mains and conduits, 218 
Leader pipes, 58 
Location of furnaces, 71 

of radiators, 124 
Low pressure steam traps, 133 

Main and riser layout, 131 

Mains, cap. of hot water, table, 361 

condensation, dripping from, 267 

diameter of, 234 

pitch of, 124 

pressure drop and diam. of, 265 

velocity of water in, 234 
Manholes, 222 
Measurement of air velocities, 32 

of heat, 10 

of high temperatures, 11 
Mechanical equivalent of heat, 13 
Mechanical vacuum steam htg. sys., 

advantages of, 142 

automatic pump for, 144 

automatic system, 149 

Dunham system, 150 

Paul system, 150 

principal features of, 143 

Van Auken, 148 

Webster system, 145 
Mechanical warm air heating and 
ventilating sys., 153, 169, 184 

blowers and fans for, 155 

definitions of terms, 169 

elements of, 153 

exhaust, 154 

heat loss and cu. ft. air exhausted, 
170 

theoretical considerations for, 169 

variations in design of, 154 
Mills system (attic main), 90, 93 
Modulation valve for Webster sys- 
tem, 147 
Moisture, addition of, to air, 30 

with air, 25 

Naperian logarithms, table, 338 
Nitrogen, 17 
'n,' values of, 47 

Operation of furnaces, 78 

of hot water heaters and steam 
boilers, 137 

suggestions for, 137 
Outside temp, for design, 79 
Oxygen, 17 



INDEX 



399 



Packless valves, 112 
Paul sys. of mech. vac. heating, 150 
typical piping connections for, 150 
Pipe coil radiators, IQi 

capacity of, in sq. ft. of steam 
radiation, 360 

equalization, table of, 359 

for refrigeration, 294 

line refrigeration, 306 

sizes, determination of, 121 
Pipe, leader, 58 

Piping connection around heater and 
engine, 200 

connections for auto. vac. sys., 149 

connections for Paul sys., 151 

for heating sys. definitions, 86 

system for automatic control of 
Webster system, 147 
Pitot tubes, 33 
Plans and speci. for htg. sys., 318 

typical specifications, 319 
Plenum system, actual amount of 
air exhausted in, 188 

air needed cu. ft. per hour in, 172 

air velocity , table, 186 

air velocity theoretical in, 184 

air washing and humidifying, 167 

amount of steam condensed, 183 

application of to school bldgs., 200 

approximate rules for, 178 

approximate sizes of fan wheels, 
table, 195 

arrangement of coils in pipe heat- 

• ers, 180 

arrangement of sees, and stacks in 
Yento heaters, 182 

basement plans for, 203 

blower fans, actual h. p. to move 
air, 193 

Carpenter's rules for, 194 

cast surface for, 161 

coil surface in, 173 

cross sectional area ducts, regis- 
ters, etc., 172 

data, table, 202 

division of coil surface in, 162 

double ducts in, 166 

dry steam needed in excess of exh. 
from engine, 183 

efficiency and air temp., table, 175 

factors for change of velocity and 
volume, table, 188 

fan drives for, 195 

final air temperature in, 179 

floor plans for, 203-205 

heating surface in coils of, 173 

heating surfaces, 159 

h. p. of engine for fan for, 192 

h. p. to move air, table, 186 

'K,' values of, 174 

layout, 163, 164 

piping connections around heater 
and engine, 200 

pressure and velocity, results of 
tests of, 189 



single duct in, 165 

speed of blower fans, table, 197 

speed of fans for, 196 

temp, of air at register in, 171 

temp, of air leaving coils, 180 

total B. t. u. transmitted per hr., 
table, 176 

use of hot water in indirect coils, 
183 

values of 'c,' 176 

values of 'K,' 174 

velocity of air escaping to atmos- 
phere, table, 187 

work done in moving air, 192 
Power plant layout, 259 
Pressed steel radiators, 103 
Pressure, absolute, 12 

and velocity, results of tests, 189 

gage, 12 

in ounces per sq. in., table, 356 

water in mains, 231 
Principal features of mechanical vac- 
uum heating system, 143 
Properties of air, table, 344 
I of ammonia, table, 380 

of carbon dioxide, table, 382 

of steam, table, 335 

of sulphur dioxide, table, 382 
Psychometric chart, 345 
Pumps, boiler feed, 249 

centrifugal, 247 

circulating, 244 
I city water supply, 249 

electric, 137 

for absorption system, 301 
I for mech. vac. steam heating, 144 

Radiation, 14 
I amount of, one sq. ft. reheater 
' tube surface will supply, 241 
amt. supplied by economizer, 253 
! amt. supplied by one h. p., 252 

hot water, 106 
I one lb. exh. steam will supply, 237 
I supplied by 1 h. p. exh. steam, 237 
i sur. to heat circulating water, 254 



surface to heat feed water, 



108 



Radiators, amt. of surface on. 
cast, 103 

classification of, 104 
columns of, 104 
direct, 87 
direct-indirect, 87 
height of, 106 
indirect, 88 

location and connection of, 124 
pipe coil, 104 
pressed steel, 103 
sizes, etc., for ten room house, 

table, 127 
sizes, table of, 108 
steam, 106 

surface calculation for, 114 
sur. effect on trans, of heat, 107 
tapping list, 358 



400 



INDEX 



Recirculating duct, 72 
Rectifiers, 298 
References, 

district heating, 270 

electrical heating, 282 

furnace heating, 84 

heat loss, 50 

hot water and steam heating, 139 

plenum heating, 206 

vacuum heating, 152 

ventilation and air supply, 38 

refrigeration, 318 
Refrigeration, 

absorbers, 300 

absorption and compression sys- 
tems compared, 302 

absorption system, 294 

absorption system, elevation of. 
296 ' 

capacity of brine cooled system, 
815 

capacities, table, 385 

circulating system, 302 

classification of systems, 283 

coils, sq. ft. cooling, 311 

cold air system, 284 

compression system, 286 

condenser, 289 

coolers for weak liquor, 301 

costs of ice making, 316 

evaporators, 292 

exchangers, 301 

gallon degree calculation, 315 

general application, 313 

generators, 298 

horse-power for, 384 

heat loss, 308 

ice making cap. calculation, 314 

influence of dew point, 305 

methods of maintaining low temp.. 
303 

pipe line, 306 

pipes, valves and fittings, 294 

pump for absorption system, 301 

rectifiers, 298 

vacuum system, 284 
Register, area of, 56 

dimensions of, table, 350 

ducts, area of, 172 

sizes, net heat, 56 

temperature, 56 
Regulation, district heating, 263 

Sylphon damper, 273 
Room temperature, standard, 47 

Salt brine solution, 384 
Service connections, 235 
Sheet metal dimensions, 353 
Single duct, plenum system, 165 
Sizes of fan wheels, approximate, 

table, 195 
Sizes of ice cans, 389 
Smoke flues, equalization of, 350 
Specifications for plans, 319 
for boilers, 371 



Specific heat, 13 

heats, etc., of substances, 355 
Speeds of blower fans, 196 
Squares, cubes, etc., table, 328 
Stacks and risers, 74 
Standard room temperature, 47 
Steam and hot water fittings, 110 

available for heating circulating 
water, 237 

boilers, 108 

condensed per sq. ft. of heating 
sur. per hour, plenum sys., 183 

dry, needed in excess of engine ex- 
haust, 183 

heater, high pressure, 244 

heating, district, 264 

loop, 135 

mains, diameter of, 265, 362 

pipe fittings, 366 

pipe insulation, 131 

radiators, 106 

traps, high pressure, 184 

used by engines, 375 
Steam system, 85 

amt. condensed in plenum sys., 183 

classification, 87 

diagrams for, 91 

parts of, 85 

second classification of, 88 
Street mains and conduits, layout, 

218 
Suggestions for operating furnaces, 
78 

hot water heaters and boilers, 137 
Sylphon damper regulator, 278 

Table 1 determination of CO2, 21 
Tables II, III volume of air per per- 
son, 23, 24 
Table IV conductivities of materials. 

40 . 

Table V exposure losses, 44 
Table VI values of t', 48 
Table VII values of to, 49 
Table VIII heat given off by per- 
sons, lights, etc., 49 
Table IX application to 10 room 

res., 63 
Table X size and sur. of rads., 108 
Table XI temp, of water in mains, 

120 
Table XII summary, h. w. htg., 127 
Table XIII vel. in plenum sys., 172 
Tables XIV-XVII efficiencies of coils, 

175, 177 
Tables XVIII-XIX temp, of air on 

leaving coils, 179, 180 
Tables XX-XXII air pressure and 

velocity. 186, 188 
Table XXIII sizes of fans, 195 
Table XXIV speeds of fans, 197 
Table XXV data for plenum sys., 202 
Table XXVI heat loss from pipes, 217 
Table XXVII pressure of water in 
mains, 234 



INDEX 



401 



Table XXVIII cal. of conduit mains, 

269 
Table XXIX transmission through 

insulation, 309 
Table 1 squares, cubes, etc., 328 
Table 2 trigonometric functions, 334 
Table 3 equivalents of units, 334 
Table 4 properties of steam, 335 
Table 5 Xaperian logarithms, 338 
Table 6 water conversion factors, 

338 
Table 7 vol. and wt. of dry air, 339 
Table 8 weight of pure water, 340 
Table 9 boiling points of water, 342 
Table 10 wt. of water and air, 342 
Table 11 relative humidities, 343 
Table 12 properties of air, 344 
Table 13 dew points of air, 345 
Table 14 fuel value of Am. coals, 348 
Table 15 capacities of chimneys, 349 
Table 16 equalization of smoke 

flues, 350 
Table ]7 dimensions of registers, 350 
Tables 18, 20 cap. of fur., 351, 352 
Table 19 cap. of pipes and reg., 351 
Table 21 area of vertical flues, 352 
Table 22 sheet metal dimensions, 3-53 
Table 23 weight of G. I. pipe, 354 
Table 24 sp. ht., etc., of substances, 

355 
Tables 25, 26 water pressures, 356 
Table 27 wrought iron pipes, 357 
Table 28 expansion of pipes, 358 
Table 29 tapping hst of rad., 358 
Table 30 pipe equalization, 359 
Table 31 cap. of hot water risers, 360 
Table 32 cap. of steam pipes, 360 
Table 33 cap. of hot water pipes, 361 
Table 34 cap. of hot water mains, 361 
Tables 35, 36 sizes of steam mains, 362 
Table 37 friction in pipes, 364 
Table 38 grav. and vac. returns, 365 
Table 39 expansion tanks, 365 
Table 40 sizes of flanged fittings, 366 
Table 41 dimensions of pipe fittings, 

366 
Table 42 friction in air pipes, .367 
Table 43 temp, for testing plants, 

370 
Table 44 spec, for boilers, 371 
Table 45 heat trans, through pipe 

covering, 372 
Table 46 factors of evaporation, 373 
Table 47 heat in feed water, 373 
Table 48 sizes of Vento heaters, 374 
Table 49 steam used by engines, 375 
Tables 50, 51, 52 speeds, cap., h. p. 

of various fans, 376-378 
Table 53 freezing mixtures, 380 
Table 54 properties of ammonia, 380 
Table 55 sol. of ammonia in water, 

381 
Table 56 strength of ammonia 

liquor, 381 



Table 57 properties of sulphur diox- 
ide, 382 
Table 58 properties of carbon diox- 
ide, 382 
Table 59 boiling points of liquids, 383 
Table 60 calcium brine solution, 383 
Table 61 salt brine solution, 384 
Table 62 horse-power for refrig., 384 
Table 63 ammonia for one-ton re- 
frig., 385 
Table 64 refrigeration caps., 385 
Table 65 cost of ice making, 386 
Table 66 temperature of ammonia, 

387 
Table 67 hvdrometer scales, 388 
Table 68 time to freeze ice, 389 
Table 69 sizes of ice cans, 389 
Table 70 temp, for cold storage, 389 
Tanks, expansion, 113, 365 
Temperature absolute, 12 

best for design, 79 

chart, 81 
Temp, control in heating sys., 271 

Andrews system, 272 

important points in, 275 

in large plants, 274 

Johnson system, 276 

National system, 278 

Powers system, 277 

principle of system. 271 

special designs of, 275 

Sylphon damper control, 273 

thermostat, 272 

of air entering plenum system, 171 

of air in greenhouses, table, 120 

of air leaving coils in plenum sys- 
tem, 179 

of ammonia, 387 

for cold storage, 389 

for testing plants, .370 

measurement of high, 11 

methods of obtaining low, 303 

room standard, 47 
Thermoflers, Belvac, 148 
Thermostat, 272 

thermostatic valve, 146 
Time to freeze ice, 389 
Traps, high pressure steam, 134 

low pressure steam, 133 
Trigonometric functions, 334 

Under-feed furnaces, 69 

Use of hot water in indirect coils, 183 

Vacuum systems, 99 

and gravity returns, 365 

of refrigeration, 2S4 
Values of 'c' 176 

of 'k,' 177 

of 'n,' 47 

of 't,' 48, 49 
Valves, air, 112 

automatic vacuum, 149 

modulation valve, 147 









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